Phoenix Shatters Records: Warmest February/Winter and Mind-Boggling March

[SnoSki14]

9 hours ago, gallopinggertie said:

Today Flagstaff had a high temp four degrees higher than their April record high…

 

Flagstaff had a higher temperature than their average July-August temperatures in March...crazy 

[GaWx]

Fwiw this article was just released:

https://www.yahoo.com/news/articles/early-southwest-heat-latest-parade-070743575.html

 Note this paragraph:

“Climate scientists at World Weather Attribution did a flash analysis — which is not peer-reviewed yet — of whether climate change was a factor in this Southwest heat wave. They compared this week's expected temperatures to what's been observed in the area in March since 1900 and computer models of a world with climate change. They found that ‘events as warm as in March 2026 would have been virtually impossible without human-induced climate change.’”

 Any opinions about this article?

[donsutherland1]

World Weather Attribution's flash analysis of the unprecedented March heat in western North America.

Excerpt:

Observation-based data products show a strong increase in the likelihood and intensity of heat waves in the region, suggesting that such events have become about 4°C warmer as a best estimate, and that events as warm as in March 2026 would have been virtually impossible without human-induced climate change. Climate models strongly underestimate this observed trend but still show a significant increase in extreme heat. We combine models and observations, giving equal weight to both lines of evidence, and find an estimated increase in intensity of 2.6°C for such events, with an increase in likelihood of a factor of about 800. This means that without climate change it would have been virtually impossible for the event to occur.

[donsutherland1]

4 hours ago, GaWx said:

Fwiw this article was just released:

https://www.yahoo.com/news/articles/early-southwest-heat-latest-parade-070743575.html

 Note this paragraph:

“Climate scientists at World Weather Attribution did a flash analysis — which is not peer-reviewed yet — of whether climate change was a factor in this Southwest heat wave. They compared this week's expected temperatures to what's been observed in the area in March since 1900 and computer models of a world with climate change. They found that ‘events as warm as in March 2026 would have been virtually impossible without human-induced climate change.’”

 Any opinions about this article?

Although the flash analysis isn't peer reviewed, it is derived from a peer-reviewed methodology, which provides credibility. These studies provide value, as they provide an alternative to pure statistical research. The corroboration between the modeling and statistics enhances the quality of their findings. Further, studies concerning prior extreme heat outbreaks in the Southwest have all found a strong link to climate change.

As for March 2026, March 2026 is poised to become Phoenix's first March to break outside the 99% confidence interval based on 30-year climate data.

 

[GaWx]

4 hours ago, donsutherland1 said:

Although the flash analysis isn't peer reviewed, it is derived from a peer-reviewed methodology, which provides credibility. These studies provide value, as they provide an alternative to pure statistical research. The corroboration between the modeling and statistics enhances the quality of their findings. Further, studies concerning prior extreme heat outbreaks in the Southwest have all found a strong link to climate change.

As for March 2026, March 2026 is poised to become Phoenix's first March to break outside the 99% confidence interval based on 30-year climate data.

 

Don and others,

 For obvious reasons I’m having trouble with what’s bolded from this article:

"The area of the U.S. being hit by extreme weather in the past five years has doubled from 20 years ago, according to the National Oceanic and Atmospheric Administration's Climate Extremes Index, which includes various types of wild weather, such as heat and cold waves, downpours and drought."

———

 This is unclear. Are they implying that cold waves have increased since 20 years ago due to CC?

[donsutherland1]

6 minutes ago, GaWx said:

Don and others,

 For obvious reasons I’m having trouble with what’s bolded from this article:

"The area of the U.S. being hit by extreme weather in the past five years has doubled from 20 years ago, according to the National Oceanic and Atmospheric Administration's Climate Extremes Index, which includes various types of wild weather, such as heat and cold waves, downpours and drought."

———

 This is unclear. Are they implying that cold waves have increased since 20 years ago due to CC?

The Climate Extremes Index includes cold. However, for the Southwest, extreme cold has disappeared in recent years. Here's the CEI's temperature charts:

[Stormchaserchuck1]

Just continues and continues

[donsutherland1]

Phoenix has now reached 100° for the seventh consecutive day. That surpasses the April record of six consecutive days from April 25-30, 1992.

Over the past seven days (March 18-24), Phoenix has had a mean high temperature of 102.7°. That tops the seven-day record for April of 101.7° that was set during April 24-30, 1992.

[donsutherland1]

To illustrate the extreme nature of the ongoing heatwave in Phoenix, there were six dates since 1980 when the daily record was broken by 8F or more. Four were: 3/19/2026, 3/20/2026, 3/21/2026, 3/22/2026. The others: 9/28/2024, 10/6/2024. 

[donsutherland1]

Phoenix: March 1-24, 2026 vs. its historical record.

[GaWx]

8 hours ago, donsutherland1 said:

Phoenix: March 1-24, 2026 vs. its historical record.

Hey Don,

 Phoenix had a high of 100 today, the 8th day in a row of 100+! Before 2026, there had been only one March day of 100+ and that was right at 100 on March 26th! Holy cow!

[donsutherland1]

2 hours ago, GaWx said:

Hey Don,

 Phoenix had a high of 100 today, the 8th day in a row of 100+! Before 2026, there had been only one March day of 100+ and that was right at 100 on March 26th! Holy cow!

And the updated chart:

[donsutherland1]

Phoenix's hottest March on record is nearing an end. This space will provide numerous highlights.  Some things that are virtually certain:

1) March 2026 will have a mean temperature that would rank it as the second warmest April.

2) Prior to 2026, the average record high maximum temperature for March 16-31 was 96.6°. The March 16-31 period will have an average high temperature that exceeds that average.

3) Phoenix tied or exceeded its March monthly record high temperature on 9 days.

4) In terms of statistical anomalies related to monthly mean temperatures, the Phoenix monthly mean temperature will easily surpass the December 2015 mean in New York City relative to each city's historical climate record.

The above is an AI-generated artistic rendition of the March 2026 heat in Phoenix.

 

[Stormchaserchuck1]

It's one of the localized events that gives me an accelerating global warming thought. 

[donsutherland1]

17 minutes ago, Stormchaserchuck1 said:

It's one of the localized events that gives me an accelerating global warming thought. 

Many cities in the Southwest and even California will have experienced their warmest March on record, some by large margins.

[Stormchaserchuck1]

14 minutes ago, donsutherland1 said:

Many cities in the Southwest and even California will have experienced their warmest March on record, some by large margins.

Yeah.. I mean Flagstaff never goes higher than 73 in March, then it hits 84 and has 4 days 80+. At 35N latitude I don't see why it can't do that, but still.

[donsutherland1]

18 minutes ago, Stormchaserchuck1 said:

Yeah.. I mean Flagstaff never goes higher than 73 in March, then it hits 84 and has 4 days 80+. At 35N latitude I don't see why it can't do that, but still.

Flagstaff has an altitude > 2,100 meters or about 7,000 feet ASL.

[GaWx]

 1. How about this? Phoenix had its coolest high in 11 days by a good margin (96) and yet it was still another record high, the 14th of this month!        

 2. Believe it or not, the next two days’ record highs of 97 are forecasted to be close to being hit. So, two more daily record highs are possible!

 3. The morning low was 75. IF it doesn’t cool down to 74 by midnight local time, it would be not only a new record high low for today, it would become the new monthly record high low and the earliest 75 low by far with the current earliest being way out on April 19th! The current record for the day and month is 74, set way back in 1986.

[LongBeachSurfFreak]

I’m not discounting this event is highly influenced by climate change, but in regards to Pheonix at least some of the temp increase is related to the UHI. I don’t see any reference to that in the data provided. Pheonix pre 1970s isn’t comparable to today.


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[GaWx]

2 hours ago, LongBeachSurfFreak said:

I’m not discounting this event is highly influenced by climate change, but in regards to Pheonix at least some of the temp increase is related to the UHI. I don’t see any reference to that in the data provided. Pheonix pre 1970s isn’t comparable to today.


.

 We’ve talked about UHI being a nontrivial portion of Phoenix’s warming. I’ve brought it up, myself.

 But, note as you may already realize that the UHI affects the warming of lows more than the warming of highs (assuming I’m not mistaken).

[LongBeachSurfFreak]

 We’ve talked about UHI being a nontrivial portion of Phoenix’s warming. I’ve brought it up, myself.
 But, note as you may already realize that the UHI affects the warming of lows more than the warming of highs.

Yeah I did not mention lows as we are all on the same page. There are some great ways to mitigate urban heat islands that are sadly underutilized. Green roofs, painting asphalt white and mitigation of suburban sprawl.
Regardless of the UHI influence (which is hard to quantify) it’s a historic and unprecedented run.


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[donsutherland1]

9 hours ago, LongBeachSurfFreak said:

I’m not discounting this event is highly influenced by climate change, but in regards to Pheonix at least some of the temp increase is related to the UHI. I don’t see any reference to that in the data provided. Pheonix pre 1970s isn’t comparable to today.


.

UHI, which is an important contributor, has been mentioned in several of the past Phoenix-related threads.  Even setting aside, UHI, there has been a strong warming trend in Arizona and the Southwest. 

During 1970-2025, Arizona's minimum temperatures have warmed an average of 0.6°/decade. Phoenix's have increased by 0.8°/decade. In terms of maximum temperatures, Arizona's rate of warming has been 0.7°/decade while Phoenix's has been 0.8°/decade. The differences are a reasonable but not perfect proxy for the impact of UHI.

The ongoing March heat is widespread. The following stations with 100-year or longer climate records are on course for their warmest March on record. Some will break their existing records by sizable margins.

[Stormchaserchuck1]

21 hours ago, donsutherland1 said:

Flagstaff has an altitude > 2,100 meters or about 7,000 feet ASL.

500mb ridge maxed out >5970dm. Combination of that and lack of snowcover in the southern Rockies made a seemingly very anomalous situation more possible. Not saying it wasn't a big pattern break though. 

[gallopinggertie]

5 hours ago, donsutherland1 said:

UHI, which is an important contributor, has been mentioned in several of the past Phoenix-related threads.  Even setting aside, UHI, there has been a strong warming trend in Arizona and the Southwest. 

During 1970-2025, Arizona's minimum temperatures have warmed an average of 0.6°/decade. Phoenix's have increased by 0.8°/decade. In terms of maximum temperatures, Arizona's rate of warming has been 0.7°/decade while Phoenix's has been 0.8°/decade. The differences are a reasonable but not perfect proxy for the impact of UHI.

The ongoing March heat is widespread. The following stations with 100-year or longer climate records are on course for their warmest March on record. Some will break their existing records by sizable margins.

Yeah, the UHI is real but it seems clear this event has been incredibly anomalous even outside of the big cities. One example is that Nogales has seen 11 record highs in a row. Nogales is a fairly small town whose population today (just under 20,000) is barely higher than it was in 1980. Looking at satellite views, you can tell there is not much paved area there (even the cross-border Nogales is quite compact) and it’s surrounded by undeveloped mountains, so it seems like a good foil to Phoenix.

[LongBeachSurfFreak]

UHI, which is an important contributor, has been mentioned in several of the past Phoenix-related threads.  Even setting aside, UHI, there has been a strong warming trend in Arizona and the Southwest. 
During 1970-2025, Arizona's minimum temperatures have warmed an average of 0.6°/decade. Phoenix's have increased by 0.8°/decade. In terms of maximum temperatures, Arizona's rate of warming has been 0.7°/decade while Phoenix's has been 0.8°/decade. The differences are a reasonable but not perfect proxy for the impact of UHI.
The ongoing March heat is widespread. The following stations with 100-year or longer climate records are on course for their warmest March on record. Some will break their existing records by sizable margins.

Great example of UHI from this morning. Approximately 80 miles apart and similar coastal locations, elevations and latitude.
KCPK 34
KFOK 13
Not to derail a great discussion. I have been following you’re great analysis of the SW climate change induced warming over the years.


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