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Last year, Phoenix experienced a historically hot summer. Although the extreme heat held off through May this year, a severe heatwave developed toward mid-June.

The June 2021 heatwave was among Phoenix's and Tucson's most severe June heatwaves and their most severe heatwave this early in the season. This heatwave developed as an extreme upper air ridge evolved during an era of rising June temperatures and an ongoing drought. An extreme heat event commenced at Tucson on June 11 and it commenced at Phoenix on June 13.

Such events are likely to become even more frequent in the years ahead. Anthropogenic warming is creating a growing likelihood of long-duration extreme events through more frequent wave resonance events (Kornhuber et al., 2016 and Mann et al., 2017).

Already, the frequency and intensity of compound summertime hot extremes (events that combine daytime and nighttime heat where such temperatures are above their 90th percentile for their calendar) has been increasing especially in geographic locations that include the U.S. Southwest (Wang 2020). The increase in forcing associated with anthropogenic greenhouse gases is the dominant driver of this outcome (Wang 2020).

Table 1: Phoenix's High Temperatures during June 12-20, 2021
Phoenix-June-HW-2021-1.jpg

Table 2: Phoenix's Average June Temperatures (30-Year Moving Average)
PHXJune2021-2.jpg

Table 3: Phoenix's Record High Maximum Temperatures
Phoenix-June-HW-2021-3.jpg

Table 4: Phoenix's Record High Minimum Temperatures
Phoenix-June-HW-2021-4.jpg

A portion of this heatwave qualified as the 8th Extreme Heat Event (EHE) on record for June, as at least 3 days saw the maximum , temperature exceed the 97.5th percentile (Phoenix: 115° or above; Tucson: 110° or above), the high temperature average exceeded the 97.5th percentile (Phoenix: 115° or above; Tucson: 110° or above), and all high temperatures exceeded the 81st percentile (Phoenix: 110° or above; Tucson: 105° or above) in June-August high temperatures for the 1971-2000 base period (Clarke, et al.,2014). The extreme heat event began on June 11 in Tucson and June 12 at Phoenix.

Table 5: Phoenix's Extreme Heat Events in June (1896-2021)
Phoenix-June-HW-2021-5.jpg

Additional Records:

Earliest 116° or above high temperature: June 17, 2021 (old record: June 19, 2016 and 2017)

Earliest 4 consecutive 115° days: June 15-18, 2021 (old record: June 19-22, 1968)

Most consecutive 115° days: 6, June 15-20, 2021 (old record: 4, June 19-22, 1968; June 25-28, 1979; June 25-28, 1990; July 26-29, 1995; July 28-31, 2020; and, August 16-19, 2020)

Earliest 4-day average high temperature of 115° or above: June 14-17, 2021 (old record: June 18-21, 2017)

Earliest 5-day average high temperature of 115° or above: June 14-18, 2021 (old record: June 17-21, 2017)

Earliest 6-day average high temperature of 115° or above: June 13-18, 2021 (old record: June 18-23, 2017)

Earliest 7-day average high temperature of 115° or above: June 13-19, 2021 (old record: June 18-24, 2017)

Earliest 8-day average high temperature of 115° or above: June 13-20, 2021 (old record: June 18-25, 2017)

Earliest mean temperature of 100° or above: June 15, 2021 (old record: June 17, 2008)

Earliest 2-day average mean temperature of 100° or above: June 15-16, 2021 (old record: June 17-18, 2008 and 2015)

Earliest 3-day average mean temperature of 100° or above: June 14-16, 2021 (old record: June 17-19, 2015)

Earliest 4-day average mean temperature of 100° or above: June 14-17, 2021 (old record: June 18-21, 2017)

Earliest 5-day average mean temperature of 100° or above: June 13-17, 2021 (old record: June 18-22, 2017)

Earliest 6-day average mean temperature of 100° or above: June 13-18, 2021 (old record: June 18-23, 2017)

Earliest 7-day average mean temperature of 100° or above: June 13-19, 2021 (old record: June 18-24, 2017)

Earliest 8-day average mean temperature of 100° or above: June 12-19, 2021 (old record: June 17-24, 2017)

Earliest 91° minimum temperature: June 17, 2021 (old record: June 22, 2017)

Earliest 92° minimum temperature: June 18, 2021 (old record: June 25, 2017)

Earliest 2 consecutive 90° low temperatures: June 16-17, 2021 (old record: June 21-22, 2017)

Earliest 3 consecutive 90° low temperatures: June 16-18, 2021 (old record: June 29-July 1, 2013)

Earliest 4 consecutive 90° low temperatures: June 16-19, 2021 (old record: July 8-11, 2020)

Most consecutive 90° low temperatures in June: 4, June 16-19, 2021 (old record: June 26-27, 1990; June 29-30, 2013; June 26-27, 2016; June 21-22, 2017; and, June 25-26, 2017)

Earliest 2-day average low temperature of 90° or above: June 16-17, 2021 (old record: June 21-22, 2017)

Earliest 3-day average low temperature of 90° or above: June 16-18, 2021 (old record: June 24-26, 2017)

Earliest 4-day average low temperature of 90° or above: June 16-19, 2021 (old record: July 4-7, 2018)

Earliest 5-day average low temperature of 90° or above: June 16-20, 2021 (old record: June 22-26, 2017)

Earliest 6-day average low temperature of 90° or above: June 16-21, 2021 (old record: June 21-26, 2017)

Highest average June minimum temperature after over 4 days: 91.0°, June 16-19, 2021 (old record: 89.8°, June 24-27, 1990; June 25-28, 1990; June 26-29, 1990; June 27-30, 1990; and, June 23-26, 2017)

Highest average June minimum temperature after over 5 days: 90.6°, June 16-20, 2021 (old record: 90.0°, June 26-30, 1990 and June 22-26, 2017)  

Tucson also experienced extreme heat. As with Phoenix, Tucson has seen a steady increase in June minimum and maximum temperatures. This outcome has increased the statistical probability of extreme heat events.

Table 1: Tucson's High Temperatures during the June 11-21, 2021 Heatwave
Tucson-June-HW-2021-1.jpg

Table 2: Tucson's Average June Temperatures (30-Year Moving Average)
TUSJune2021-2.jpg

Table 3: Tucson's Record High Maximum Temperatures
Tucson-June-HW-2021-3.jpg

Table 4: Tucson's Record High Minimum Temperatures
Tucson-June-HW-2021-4b.jpg

Table 5: Tucson's Extreme Heat Events in June
Tucson-June-HW-2021-5.jpg

Additional Records:

Most consecutive days with high temperatures of 110° or above: 8, June 12-19, 2021 (old record: 6, June 24-29, 1994)

Most consecutive days with high temperatures of 111° or above: 7, June 13-19, 2021 (old record: 6, June 24-29, 1994)

Most consecutive days with high temperatures of 112° or above: 7, June 13-19, 2021 (old record: 4, June 25-28, 1990)

Highest average high temperature over 8 days: 112.5°, June 12-19, 2021 (tied record set during June 23-30, 1994)

 

Updates:

Phoenix has its hottest June on record

 

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Hey Don -

thanks for all this recap and refinement in data delivery. Always appreciated ( and fascinating ) in/during significant event postmortem

"... The June 2021 heatwave was among Phoenix's and Tucson's most severe June heatwaves and their most severe heatwave this early in the season. This heatwave developed as an extreme upper air ridge evolved during an era of rising June temperatures and an ongoing drought. An extreme heat event commenced at Tucson on June 11 and it commenced at Phoenix on June 13..."

Quick comments, one anecdotal, one observed/philosophical, respectively: 

One ...  I've often mused that heat waves in July and August, as extreme as they are, are actually manifested under an' insolation disadvantage' - so to speak, compared to that June 7 thru July 7 span. Those latter ones manifest in a more favorable circulation medium, but are missing the pinnacle solar.  Don't say that to the dead souls of 1995 Hades On Earth Chicago heat wave that didn't make it - unfortunately, the enormity of that event is still a false equivalence to the absolute scalar potential of what "could have happened" if all that set up on June 20!

That's another in the myriad of those interesting sort of 'tendency checks-and-balances' that miraculously save Earth ( and there are very many in other physical domains ). Seasonal lagging by a month or more, protects the hemispheres from the hostility of the hottest potential; at the other end, the deeper cold arrival tends to occur when the sun's already coming back. In a 'hippy' sense, Kumbaya for life to have those extremes tend to soften if we want to get into the Goldilocks discussion.   But, sometimes these "rules" break -

Two ... The 'heat dome' out was was actually the ridge that gave us the unusual five days of 90 up here in NE U.S. the week prior;  it retrograded toward the west and slipped right under Chicago ( while changes in a Rossby wave order rolled-out over southern Canada ) to where it then re-anchored over the SW.  

This all reminds me of non-lineary wave arguments..   For the general read - the ridge it's self is not like an object being moved around in circulation super-structures. What's actually happening is that the forcing that creates the ridge is moving west; that force is non-linear wave function/forcing. It has to do with transitive wave-mechanics, where on-going activity at point A acts like a wave-guide and drives the emergence of wave structures at point B, with no apparent or observable connection between the two points in space.  You get that in fluid dynamic systems...etc.  As a separate point of interest, when no observable connection results in sudden wave emergence in the ocean - for example - this is can lead to rogue-wave phenomenon.  And so the ridge really was forcibly emerging west relative to the flow - it gives the allusion of the ridge bodily moving west. Troughs do the same - in fact, ridge-trough couplets compose a single wave length, but the non-linear forcing can favor one or the other. All retrograde motion is in fact 'support shifting'  It's why those are the most difficult leading times in deterministic Meteorology, because retrograde is synonymous with non-linearity activity and that is by nature .. 'invisible' as a governing motivator.  These take place more frequently in the atmosphere, because the atmosphere is less dense and is moving faster.

My personal 'hypothesis' is that the biggest events take place when non-linear, and linear wave forcing mechanics super-impose constructively within the same spatial domain. The linear is infer-able via the EOF suggestion/correlation ( teleconnectors like PNA ..AO/EPO/NAO/WPO ... MJO etc...although the MJO is in fact a wave strength index; being MJO is a wave, probably does play a mathematical roll in inducing these...).   Non linear contribution is the 'positive bust' so to speak. Or, in other facets, for lack of better description, it is like that 'feeling' you get that the EPO is going to balloon - then it happens.  But why?  It may be some form of intuitive insight as to these 'spooky actions' at a distance - rip from Quantum Mechanics but is seems apropos.

Non-linearity may in fact become linear, too, through the physical boundary of the emergence, the other side of which is synergistic result set hat has become real.

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23 minutes ago, SnoSki14 said:

Get ready to make another thread for the next record heat wave in the Pacific NW. 

Seeing 110-115+ readings on some model outputs for Washington & Oregon.

Quick glance at the 0z Euro and GFS and both are showing a max temperature in Washington state next week of 120 or above. The state record is 118.

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4 hours ago, Bhs1975 said:

The new norm baby.

Unfortunately, the advance coverage in the Seattle Times omits the role climate change is playing in increasing the likelihood and severity of such events.

https://www.seattletimes.com/seattle-news/weather/cooler-temps-arrive-tuesday-and-wednesday-but-seattle-could-see-100-degree-weekend/

Good coverage provides the “why,” which is more than the specific synoptic pattern. 

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This is one of the largest weather forums in the US, and yet we have literally no active members from the deserts of California or Arizona. Presumably...they just don't care that much. Extreme warmth or not, there is something of a diminishing return to all of this. If you're used to 110 degrees, 115 or 120 doesn't seem like much more. Going from 80 to 90 in May always feels much worse than the 90 to 100 jump for me in June. The warmth forecast in the Northwest is actually much more impressive in that regard. It's hard to argue Phoenix is becoming unlivable or something akin to that when it keeps seeing such rapid population growth. Historically, a lot of strongest western heat waves are bunched together in brief 3-5 periods. So it doesn't really shock me to see another warm period. On net, with the cooler May, it's still easily possible (and likely) we'll have a much colder warm season overall than last year in the Southwest, which was nearly wall to wall hot late April to early September.

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Ongoing climate change is driving an increase in Phoenix's temperatures. That increase is making hot synoptic patterns even hotter than they would otherwise be. In addition, one is witnessing a profound change in the ratio of hot days that exceed the 95th percentile for heat to cold days that exceed the 95th percentile for cold. The former is rising steadily. The latter has nearly disappeared (using 1971-90 percentile rankings).

Phoenix-95th-Percentile-Days-1950-2020.j

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@donsutherland1, excellent analyses from one of the best and most objective analyzers of data here.

 As much as I like your posts ITT, I think they would have been even better if you had mentioned the very likely additional significant role of UHI on mainly Phoenix’s minimum temperatures. I assume you’d agree that UHI has contributed much more to higher minimums than to higher maximums and is I believe the main reason why minimums have increased by a significantly higher amount vs the increase for maximums. So, I feel that higher minimums are due to a combo of UHI and AGW, with each having significant effects.

 For this reason, in order to get the best feel for AGW’s effects independent of UHI, I tend to focus only on maximums as I believe that the vast majority of those increases has been due to AGW. To be fair, you have focused much more on those.

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21 hours ago, donsutherland1 said:

Ongoing climate change is driving an increase in Phoenix's temperatures. That increase is making hot synoptic patterns even hotter than they would otherwise be. In addition, one is witnessing a profound change in the ratio of hot days that exceed the 95th percentile for heat to cold days that exceed the 95th percentile for cold. The former is rising steadily. The latter has nearly disappeared (using 1971-90 percentile rankings).

Phoenix-95th-Percentile-Days-1950-2020.j

Lines up well with population increase

Annotation 2021-06-24 125336.jpg

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19 minutes ago, FPizz said:

Lines up well with population increase

Annotation 2021-06-24 125336.jpg

 It appears you're indirectly referring to UHI, which I think is a legitimate significant factor for Phoenix in addition to AGW as I mentioned. But keep in mind that UHI mainly affects minimums. The increase in average maximums is likely mainly related to AGW imo and Don mainly emphasized maximums.

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14 minutes ago, GaWx said:

 It appears you're indirectly referring to UHI, which I think is a legitimate significant factor for Phoenix in addition to AGW as I mentioned. But keep in mind that UHI mainly affects minimums. The increase in average maximums is likely mainly related to AGW imo and Don mainly emphasized maximums.

I'm saying that it lines up pretty well.  In NYC for example, there has been a large population for many years (3.3 million+ in 1900).  In Phoenix, not that long ago the population wasn't very much.  In 1950, it was only 106,000.  Now it is 4.5 million.  That is a huge increase in 70 years with tons and tons of development and significant changes in the areas landscape.  I think it might play a role with daytime highs as well along with AGW. 

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2 hours ago, GaWx said:

@donsutherland1, excellent analyses from one of the best and most objective analyzers of data here.

 As much as I like your posts ITT, I think they would have been even better if you had mentioned the very likely additional significant role of UHI on mainly Phoenix’s minimum temperatures. I assume you’d agree that UHI has contributed much more to higher minimums than to higher maximums and is I believe the main reason why minimums have increased by a significantly higher amount vs the increase for maximums. So, I feel that higher minimums are due to a combo of UHI and AGW, with each having significant effects.

 For this reason, in order to get the best feel for AGW’s effects independent of UHI, I tend to focus only on maximums as I believe that the vast majority of those increases has been due to AGW. To be fair, you have focused much more on those.

Yes, UHI has played an important role with the rising minimum temperatures. That’s why I suspect that minimum readings have increased faster than maximum ones.

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I was looking the other day. Since the last big heat wave in the Northwest, Seattle has gone from 30% to 40% or so of homes with air conditioning. You can compare that to 86% of homes in Phoenix with air conditioning. That's why I actually think you may see some deaths from the heat in the Northwest in the coming days. One nice trade off for the synoptic changes happening now is the heat wave is over here, and we're getting a lot of rain the next few days. Any day with a high under 80 is a victory this close to the solstice here. I'll probably head up to one of the mountain towns to experience some early Summer 60s-low 70s.

AZ-energy-consumption.jpg

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Continuing the discussion of the point made about changes in minimum temperatures, there is also a climate change component involved with the UHI Effect Here’s one paper on that topic that explains what is happening:

https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.4688

In sum, the combination of climate change and the UHI Effect have led to more rapid warming at night.

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We are under the heat dome big-time now, in southern BC as well as the Pac NW region. 

For BC, the all-time record highs are 44.4 C (recorded as 112 F) in July 1941 at locations in the Fraser canyon region about 150 miles northeast of Vancouver. Numerous other inland locations have recorded extremes between 42 C and that value, a few of them since we converted from F to C in the late 1970s. Canada's all-time high is just one F deg higher (113F which is 45.0 C) and that was in July 1937 in towns southeast of Regina SK. In both the 1936 and 1937 heat waves, numerous 42-44 C readings were registered and the all-time warmest top thirty (available on wikipedia) is dominated by these three events (1936, 1937, 1941) despite the warming trends recently. For whatever reason Canada has not seen any new extremes, a couple of times around 2003 and 2009 there were 42C readings. Toronto has about a dozen days with 100+ readings, the hottest were in 1936 (three at 105F) and almost all the rest between 1911 and 1953. Only 2011 contributed one to this list after 1953. There has been an increase in mean temperature at Toronto but almost all of it is with overnight lows, not daytime highs (compared to the mid-20th century, obviously all parameters increased from late 19th to early-mid 20th). 

This current heat wave appears capable of approaching those all-time record highs, will report back on the results. We are right under the heart of this 500 mb heat dome (shown at 599 dm) in south-central BC this weekend. I live about halfway up the west side of the Columbia valley where the base elevation is about 400m asl and the local peaks in the Monashee range are around 2000-2500m. My local elevation is about 1050m. The nearest reporting station (Warfield BC) is at about 700m. It can be one of the province's hottest reporting sites, Osoyoos near the US border in the Okanagan and Lytton or Lillooet in the Fraser canyon are more frequently tops. We weren't quite under the full effect of this on Friday but already it was 36 C (97 F) at Warfield. Expecting closer to 40 C today and the peak likely around Monday-Tuesday. 

A/C is not all that common in our part of the world despite the fact that almost every summer there are a few sweltering days. It does tend to cool off fairly well at night here, I was out at midnight admiring the rising moon near Saturn, and it was quite comfortable, probably about 65F. If you have clear skies where you live tonight, have a look between midnight and 0200h local time, you'll see the Moon very close to Saturn and then Jupiter off to the left rising a bit later. The Moon will then be close to Jupiter on Sunday night. 

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PHOENIX HAS HOTTEST JUNE ON RECORD

Last year, Phoenix experienced a historically hot summer. Although the extreme heat held off through May this year, a severe heatwave developed toward mid-June.

The June 2021 heatwave was among Phoenix's and Tucson's most severe June heatwaves and their most severe heatwave this early in the season. In large part due to this extreme heat event, Phoenix recorded its warmest June on record.

June Statistics:
Average high temperature: 108.2° (2nd)
Average low temperature: 82.5° (1st)
Monthly mean temperature: 95.3° (1st)

Table 1: 10 Warmest June Cases
Phoenix-June-2021-Monthly-1.jpg

Table 2: Progression of June Monthly Records (Averages)
Phoenix-June-2021-Monthly-2b.jpg

Table 3: Average June Temperatures (30-Year Moving Average)
Phoenix-June-2021-Monthly-3.jpg

Table 4: Phoenix's Record High Maximum Temperatures
Phoenix-June-2021-Monthly-4.jpg

Table 5: Phoenix's Record High Minimum Temperatures
Phoenix-June-2021-Monthly-5.jpg

 

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On 6/24/2021 at 8:24 PM, raindancewx said:

I was looking the other day. Since the last big heat wave in the Northwest, Seattle has gone from 30% to 40% or so of homes with air conditioning. You can compare that to 86% of homes in Phoenix with air conditioning. That's why I actually think you may see some deaths from the heat in the Northwest in the coming days. One nice trade off for the synoptic changes happening now is the heat wave is over here, and we're getting a lot of rain the next few days. Any day with a high under 80 is a victory this close to the solstice here. I'll probably head up to one of the mountain towns to experience some early Summer 60s-low 70s.

AZ-energy-consumption.jpg

50 deaths reported in Portland from the heat

 

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On 6/24/2021 at 11:49 AM, GaWx said:

@donsutherland1, excellent analyses from one of the best and most objective analyzers of data here.

 As much as I like your posts ITT, I think they would have been even better if you had mentioned the very likely additional significant role of UHI on mainly Phoenix’s minimum temperatures. I assume you’d agree that UHI has contributed much more to higher minimums than to higher maximums and is I believe the main reason why minimums have increased by a significantly higher amount vs the increase for maximums. So, I feel that higher minimums are due to a combo of UHI and AGW, with each having significant effects.

 For this reason, in order to get the best feel for AGW’s effects independent of UHI, I tend to focus only on maximums as I believe that the vast majority of those increases has been due to AGW. To be fair, you have focused much more on those.

thats what I do too, to compile lists of our hottest summers, I use two factors (and thus generate two lists) 1) average of all maximum temps and 2) number of 90 degree highs

 

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11 hours ago, TimB84 said:

Not sure where to put this, but Death Valley hit 130 yesterday, making it two years in a row of reaching possibly the hottest temperature credibly recorded on earth.

Yesterday’s 130.0 was a bit higher than last year’s 129.9.

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11 hours ago, TimB84 said:

Not sure where to put this, but Death Valley hit 130 yesterday, making it two years in a row of reaching possibly the hottest temperature credibly recorded on earth.

The frequency of days with highs of 120+ and 125+ has increased in recent decades at Death Valley. 30-year averages and the 3 most recent years:

image.jpeg.ba519d7c66d8291a0eb60934c0967b66.jpeg

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4 hours ago, LibertyBell said:

omg finally a true 130 reading!  This is a historic moment!

I heard today the old record of 134 could be challenged and the peak of the heat will be Monday?

 

Today will very likely be hotter than tomorrow. The 134F is a flawed report. So is the 131F that was reported in Tunisia.

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