TheClimateChanger

A little skeptical of the quality of that reading, unless it was 110 at lower elevations. 1911 has a bunch of the high readings - wonder if the station used was at a lower elevation at that time, or substandard exposure. The 93F reading is a June monthly record high, however. The prior June record is 92F last set on June 26, 1952.

Several records set or tied today, including Cleveland, Detroit, Toledo, Saginaw, and Mansfield. The 96F reading at Saginaw was the warmest of any day in the past 13 years. Alpena set a new daily record high of 97F. If it stays at or above 79F through midnight local time, it will set a new all-time record high minimum & the daily mean (average of high and low) would be the second highest in the threaded record behind 88.5F on August 25, 1948.

Saginaw is now on day two of exceeding its previous all-time record high minimum. Crazy stuff.

Thanks for the heads-up, Don. I've been tracking the heat - and it's no joke! Lots of monthly high record minimum temperatures, and even several all-time records, at locations with 100-150 year PORs. Hayward in rural northern Wisconsin only dropped to 80F, breaking the monthly record by 5F and setting a new all-time record! That would only be 1F shy of the all-time June record in Manhattan! Green Bay, at 79F, set a new all-time record and tied the monthly record high. Saginaw, Michigan beat its all-time record (for any month) by 2F! Crazy stuff.

Wow! I didn't even realize it was that hot in Michigan. The low of 80F at Saginaw breaks the all-time record high minimum temperature there by 2F. The old record of 78F was set on July 1, 1931 & August 1, 2006. The old monthly record of 77F was last set on June 30, 2018. The low of 79F at Flint breaks the monthly record high set on June 20, 1953 by 1F, and ties the all-time record high minimum of 79F, set on July 18, 1942. Lansing Area, with records dating to 1863, also set a new monthly record high minimum and tied the all-time record minimum of 78F. The prior June record of 77F was last set on June 30, 2018. The all-time record of 78F was set previously on July 18, 1942 & August 1, 2006. The low of 80F at Holland, ties the June monthly high last set on June 15, 2022. The low of 77F at Houghton Lake set a new monthly record high. The old record was 75, set on June 30, 2018. The low of 78F at Detroit was one shy of the monthly record in the threaded history. It was 79F on June 25, 1952, when observations were taken at City Airport. Incidentally, it matched that reading at City Airport this morning. The all-time record is 80F, set 4 times in July and once in August, with the most recent occurrence being August 1, 2006.

Looking at some lows this morning. New monthly record high at Saint Cloud, Minnesota (80F). Minneapolis-St. Paul, Rochester, and Brainerd all fell one shy of the monthly record, but each set daily records. Wisconsin put up some insane numbers. These are all ThreadEx sites with long PORs. All subject to being maintained through midnight local standard time, which should be the case barring something unexpected. Hayward had a low of 80F, obliterating the prior monthly record of 75F by an insane 5F. The old record was last set on June 23, 2005. Also sets a new all-time record high minimum temperature. La Crosse had a low of 80F, tying the monthly record set on June 29, 1931. Green Bay had a low of 79F, breaking the monthly record of 78F last set on June 30, 1931. It also ties the all-time record high minimum temperature. Wausaw had a low of 78F, breaking the monthly record of 77F set on June 28, 1931. This was 1F below the all-time record of 79, set in 1999. Rhinelander had a low of 76F, breaking the monthly record of 75F set on June 27, 1991, and tying the all-time record high minimum temperature.

Wow, that's crazy. That would be very near the State record high minimum for the month of June if legit. Won't count though since it looks like an AWOS site. Looks like the highest is 87F at Canby from 6/29/1931. The 87F from St. Peter on June 30, 1921 is clearly wrong. The next closest low in the State that day was 75F in downtown Minneapolis (see below); however, the 87F from the 1931 heat wave looks reasonably legit. Below are ALL observations of a minimum of 83F or higher in the month of June. The 86s from 1890, 1942 & 1996 all look incorrect as well. While data from 1890 is limited, the second hottest was 73F at Saint Paul downtown, and it shows a ridiculous 4F diurnal range way out of line of the other observations. June 30, 1921 - just showing the hottest sites here: June 27, 1890 - all data:

Looks like the low so far has been 82F at Minneapolis (MSP), which is a daily record high minimum but 1F shy of the all-time monthly record in the threaded history. I do feel like there were periods in some of these recent years where MSP (and many of the larger airports) would be several degrees above surrounding observations. But they've been running much more in line with other observations, so no 84F or 85F in the cards today. Seems like they eliminated a lot of that so-called "urban heat island" effect. Don't expect these airports to pop a 100F in this heat wave when every other observation is 95-99F. It's going to need to be near 100F areawide (like 98-101F) to see a 100F observation. They've got these ASOS readings finetuned to a harder mode now. Either way, still setting a lot of records out there.

We will have to wait and see if the 79F reading holds at Green Bay, that would set a new June monthly high and tie the all-time record high.

Also, the low of 80F at Eau Claire, Wisconsin was 1F shy of both the June monthly record high minimum and the all-time record high minimum. La Crosse, Wisconsin was 1F shy of the monthly & 2F below the all-time record. Possibility that one or both gets set or tied tonight/tomorrow if the winds stay up enough. Also would need to stand through midnight local time. Not sure if there’s a risk of convection there tomorrow.

Haven't looked elsewhere but it looks like MSP has at least tied the daily record. St. Cloud has set a new daily record.

Cedar Rapids, Iowa (78F) will also be a new monthly record high minimum if it holds.

Meanwhile, a number of record high monthly minimum temperatures set in the Plains from stations with threaded records extending into the 1800s. No doubt a lot more out there. These are only the ones I checked. I didn't look at any shorter POR sites. This ridge definitely seems to be getting its act together. High temperatures reached at least as high as 108F (Saint Francis, KS) yesterday. Not quite up to 2012 levels out there, but certainly a little more than the "it's just summer" narrative would seem to imply.

There are probably more. Those are just the sites I checked. MSP was 82F overnight, but has since dropped lower due to thunderstorm activity.

Morning thoughts:

Not at Detroit, it isn't. The long-term mean is June 18th. Three years saw 0 90+ days (1882, 1907 & 1915), and therefore aren't included in the analysis.

Lol, I remember you mentioning that earlier this winter I believe. The highway probably is probably situated in a low-lying area below the airport. I mean airports tend to be on somewhat higher ground for obvious reasons. I actually remember you mentioning that earlier. In the original post, you noted your car thermometer generally runs higher - which, of course, makes sense as, in most cases, heat would be radiating from the pavement/asphalt. But you know when there wouldn't be much heat flux? Hmm, probably near sunrise in midwinter. In fact, under optimal radiational cooling, the roadway surface would actually drop below the air temperature. You are comparing a thermistor, which certainly isn't as accurate as a platinum resistance thermometer, to begin with, that's housed about 1 foot off the ground to a 2M surface temperature. It doesn't surprise me under those conditions; it would read several degrees lower. It's sampling air way below the proper height and in a local "frost hollow" south of the airport. You do realize that, under optimal radiational cooling, there can be a substantial temperature inversion in the lowest several feet of the atmosphere above the ground, right? That's why it can be in the mid/upper 30s at 2M, but with frost laying on the ground.

Perhaps the funniest thing, it didn't even reach 100F for any hour during last June's heat wave. Maybe the dewpoints are being overdone here for the upcoming stretch? Peak monthly heat index was below 85F in June 1976, 1977, 1985, and 2023. Edit: I do believe the 2023 figures are missing some observations, as there were a few hot days early in the month where the heat index must have been near 90F. The other three look correct, as monthly highs were 83-85F. Second edit: RE: 2023, I calculate a peak HX of 87F at 2:51 p.m. on June 3 [temp. 89F, Td 54F]. Going back through last year's heat wave and, yes, the peak hourly HX appears to have been 98F at 3 p.m. on the 17th [temp. 94F, Td 67F]. For additional context:

Since 1945, yes. Early data is actually from AGC, not PIT. With that said, there are some missing hours, and this would exclude any intrahour observations.

I don't think the NWS uses a specific temperature occurrence to rank summers. They track days over 90F, as they do lows and highs under 32F and lows under 0F in the wintertime, but seasonal rankings have always been by the average mean temperature (average of maximum and minimum).

You can have 90F with dewpoints in the 40s and 50s, and that's not hot at all. Wet bulb is the superior measure IMO, and I bet the elevated summer minima years have higher wet bulb averages than the years with high maxima but more typical minima. Above about 87-88F, it's almost certainly fatal.

Even if it only gets to 92-94F, if dewpoints reach into the mid 70s, that's impressive and rare. Peak heat indices could approach hourly records for the month of June, potentially on multiple days. The highest hourly heat index reading in June (dating back to 1945) is 106F at 2 pm on June 27, 1978. More recently, a bunch of overnight and morning hourly record high heat indices were set on June 29, 2012. Even more recently, a couple of late evening record values were tied on June 15, 2022. Not a forecast but just providing some context. Lots of "it's just summer" comments again on X, as though these values are commonplace every summer. Also, lots of comments complaining about the "heat index" as if it was just invented yesterday and hasn't been a thing since the 1970s. And, before that, they had the "Temperature-Humidity Index" in the 1950s to 1970s. Here's what KDKA is showing. Not saying it's correct, but if it's in the ballpark, this is "not just summer" IMO. The combination of heat and humidity would approach or exceed records from the last eight decades on multiple days. In July and August, not quite as big a deal. But this is not something you see every June, even if we did have a similar stretch last year [albeit with generally lower dewpoints]. Maybe the temperatures and/or dewpoints are being overestimated by the models and forecasts. That would be like saying multiple days in a row in late December with -20F or lower windchills is "just winter" in Pittsburgh.

I'm not cherrypicking anything. Just looking to learn more about the DTW urban heat island. Those temperature variances strike me as primarily a function of elevation and latitude. Urban heat island may add a small component. White Lake is several hundred feet higher in elevation and, as you said, 40 miles northwest. FNT and MBS are way to the north, and FNT is also a few hundred feet higher in elevation. Even Ann Arbor gains elevation, although it might be small if along Allen Creek. Of course, if the station is near the creek, it would likely be in a particularly cool microclimate for radiational cooling conditions.

You should be very pleased with my Michigan round-up then! You are the one who has thrown out comparisons to White Lake, Flint, Saginaw, and Ann Arbor in the past - all of which were warmer than DTW in my summary, some by several degrees.