TheClimateChanger

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.

It will be interesting to see where June 2025 stacks up when all is said and done. The Accuweather forecast for Carnot-Moon, PA for the rest of the month would imply the final mean temperature would come in around 73.3F. That would be the hottest June recorded at the airport, and the hottest in the threaded record since 1943. While it would only tie for 10th hottest in the threaded record, it would be 4th hottest since 1898. Six of the top 10 are during Pittsburgh's temperature steroid era of the late 1800s. Last June finished at 72.8F and was the warmest since 1994 & 3rd warmest overall at the airport behind 1967 & 1994. As an aside, if you search "Pittsburgh International Airport" on Accuweather, it actually generates the forecast for Pittsburgh Central Business District instead of Carnot-Moon or Findlay Township. So I didn't use those higher figures [that forecast would imply a final mean checking in at a whopping 73.8F!]. With that said, I do suspect the Accuweather forecast is a little overdone and would favor a final mean temperature around that of last June.

It was two separate sites. Baraga 1N was 60/20; and Wetmore was 66/20. Even Gaylord in the lower Peninsula was 72/49, so there was a wide disparity from south to north.

Good post. Although I do disagree with this part: "While at this juncture it doesn't look like record highs are in jeopardy..." Below, is the current point-click forecast centered on DTW Airport. Record highs for Saturday through Tuesday are: 96, 98, 95, and 97. Record high minima are: 75, 73, 74, and 74. So this forecast would imply a new record high on Monday, June 23, and record high minima on Sunday, Monday, and Tuesday (tie). So I don't agree with that conclusion. Clearly, records are in jeopardy or else the NWS forecast is out to lunch. And this is just one location. I'm sure other locations will be at or near record high temperatures as well.

Wow, that line/system looks quite intense. Have to wonder if it will reach derecho criteria.

Wow, I was going through some old weather records. I know @michsnowfreakreally likes to talk about old heat records, but he seldom mentions the old cold records, including a low of 20F on July 1, 1903, at Wetmore and Baraga (both in the Upper Peninsula of Michigan). I was looking at the Wetmore (near Munising) observations for that month, and wow, I want this injected in my veins. This is incredibly beautiful weather for the month of July, with 4 of the first 5 nights at or below freezing. A mean high temperature of 64.4F, and a mean low temperature of 42.3F. Doesn't get much comfier than that.

Yeah, and so? At Pittsburgh, there have only been two months since June 2023 that have been colder than normal (January and May 2025 - the latter took until the 31st to eek below the average).

Definitely some warm lows in recent nights across the Buckeye state. Several locations were not far from record warm daily minima yesterday, with New Philadelphia area tying the record warm low of 69F, set previously in 2022, 2018 and 1994.

Looking at the Michigan roundup from yesterday, a number of locations saw temperatures climb at or above 90F, including as hot as 92F at Auburn 2NE. Unfortunately, the urban chill island of Detroit could only muster a disappointing 86F. Going to be another one of those summers, where @michsnowfreak is bragging about the lack of 90F heat, whilst complaining about urban heat islands, all the while rural areas where nobody lives rack up plenty of 90s. In order for Detroit to record some readings in the 90s, it looks like some rural parts of the State will need to reach well into the mid 90s, even upper 90s. Maybe a tall ask.

Yeah, I think there was a lot of deforestation in that era. Looking at old pictures of the city, and there is not a tree to be found. Whole hillsides just stripped barren. Must have been a lot of landslides and flash floods.

With the very warm lows, could be one of the hotter 4-day stretches in the month of June by mean temperature. These are the 10 highest 4-day mean temperatures in the threaded history. Last year's heat, while falling short of the early 99-101F type forecasts, was still one of the hottest 4-day stretches on record for June. 8th officially, but several of those are duplicates from heat waves that lasted more than 4 days, such that only 4 different years saw hotter 4-day means.

Speaking of volcanos... this looks promising:

I added a little context after your quote:

I think it probably depends on whether you are looking pre- or post-invention of air conditioning. Prior to the invention of air conditioning, I suspect something near pre-industrial is the optimum. Perhaps somewhat colder. Last glacial maximum is probably too cold due to the expansive continental ice shelves, although it would open up a lot of new coastlines. Ben Franklin considered 47-50F annual mean temperature to be the ideal for agriculture and industry. I think patterns of development [prior to air conditioning] support that, with large cities like Chicago, Detroit, New York, Boston, Pittsburgh, Cleveland, Buffalo, etc. falling in that isothermal band. The south was mostly underdeveloped rural/agrarian lifestyle. Maybe some winter homes in Florida. So, prior to the invention of air conditioning, you would probably want to find the climate regime that maximized the areal extent of mean temperatures from the mid 40s to low 50s. Of course, now, most of these places are above 50F in the running means. But he did say 50-53F was the second best temperature band.

Makes sense to me, and I've made this argument in the past. If you read weather records from that era, the general consensus was warming from past eras. I think this is supported by longer-range temperature records and reconstructions. But it does call into question the use of this era as some sort of special baseline. The true baseline may, in fact, have been a continuation of the natural cooling trend that had generally characterized the period since the Holocene Thermal Maximum - perhaps to levels even colder than those of the so-called Little Ice Age. Granted the degree of warming at that time was a tiny fraction of what we see today, so it wouldn't make a huge difference. But this paper would suggest the cumulative human impact is at least slightly higher than commonly reported from temperature datasets which use that period of history as the baseline of a natural climate.

Just ran that by it. It suggests a combination of temperatures near 110F, 75 mph winds and extremely low relatively humidity likely desiccated the crops. It suggests such conditions could wilt and brown the corn, causing drought or freeze-like damage to the crop. The strong winds would have also damaged the crop and caused more heat damage than would occur in a still atmosphere.

I ran this scenario by AI and it concluded the temperature could have reached no more than about 100-110F. It said the warming from a heat burst [compressional heating] would be no greater than the dry adiabatic warming rate, and that a surface temperature of 140F would require an upper atmospheric temperature that would be implausibly high. It suggested the burst thermometers were likely the result of instrument failure due to the sudden change in temperature. Not sure if any atmospheric scientist might want to weigh in.

You can see the rural effect warming in your data for Caribou, Maine as well. Another remote community near the Canadian border. Look at all those record-breaking June temps in recent years! The complete opposite of what the UHI lie would suggest!

I would argue it translated to the surface in 2022 & 2024, as well. If you look at Bradford, PA, useful as one of the more remote and sparsely populated locations, in the Eastern CONUS. We see it had never hit 90F in the month of June dating back to 1958 in the month of June prior to 2022. The monthly record of 89F was tied in 2021. In 2022, it reached 90F twice - including a record-breaking 93F on the 22nd. It reached 90F last June an incredible three times! Additionally, it reached 89F once each in 2022 & 2024 (the former monthly record high). Just an astounding run. I expect more record-breaking heat in the mountains of northern Pennsylvania with this upcoming heat ridge. What was once without precedence is now a yearly occurrence! I like to think of it as rural effect warming. Certain persons/entities claim warming is being enhanced or caused by a so-called urban heat island effect, but then when you look at the actual numbers, it's often the most remote locations breaking records all the time. So, the urban heating theory makes no sense. If anything, modern technology and siting/exposure standards are such that the UHI signal is less impactful as it was in the past.

Yeah, I doubt there's ever been a case where the entire region was AOA 100F on the same date.

Some scenes from the flash flood emergency on Sunday:

Looks increasingly likely that it turns hotter by Sunday. The NWS forecast has low 90s. I took a look at the most recent GFS run and, taken literally, it would suggest 90s Sunday-Friday. Obviously, not ready to commit to that forecast, but either way it should be a hot week. Hopefully, it will be drier as well, with all of the recent rainfall and flooding issues. A very soggy weekend for the US Open Championship at Oakmont.