TheClimateChanger

Table attached below shows the difference between mean low temperature for 1st 22 days of July 2025 versus mean low temperature for July 2024. 51 sites have data for both years. Missing data not a significant factor, only 7 of the sites have more than 3 days missing through the 1st 22 days of the month. It is a factor for some individual sites, e.g. Pike Island shows an 8.7F increase but had 15 missing days in July 2024. 49 of 51 warmer. Exceptions: Donegal 2NW Coop, bizarrely 3.3F cooler, and DUJ Airport, 0.5F cooler. The mean difference is +3.2F across the 51 sites. 4 of the 6 smallest increases are the airport sites - DUJ (0.5F cooler), AGC (1.0F warmer), MGW (1.4F warmer), and PIT (1.7F warmer). Compared to the mean (average) change across the 51 sites, DUJ is 3.7F cooler, AGC is 2.2F cooler, MGW is 1.8F cooler, and PIT is 1.5F cooler. The smaller airfields seem to be unaffected. AFJ is +5.6 for the year on year (or 2.4F warmer than the mean change) and BTP is +4.1F for the year on year comparison (or 0.9F warmer than the mean change).

I don't know what's going on with the airport thermometers this year. It's bizarre. Like all the airports dropped 2-3F, every single one of them? Especially AGC and HLG. They went from one of the warmest spots in the PBZ CWA last July to among the coldest by mean maximum temperature this year? AGC has suddenly become one of the coldest spots in the entire CWA outside of some high mountain sites for daily high temperatures. PIT airport went from 1.7F warmer than the Moon Township COOP in July 2024, to 0.9F colder this July. The lows are still warmer, but they have dropped a bunch too relative to the COOP sites. Last year, 4 airport sites had the warmest daily low temperatures in July. This year, the highest is like 5th of all sites.

Record warm daily minimum of 72F tied yesterday in St. Cloud, Minnesota (records since 1893). Saw several other sites that had their second or third warmest lows for July 23. Should see multiple records over the coming days across the central U.S.

The ranges are HUGE as well - there is a BIG difference between 2C and 4C of temperature change up or down. I mean the last glacial maximum was only about 5-6C colder than preindustrial. Using 2025 at the baseline, it was 2C+ cooler just a few hundreds of years ago. So I'm pretty sure we could weather 2C of gradual cooling with no major repercussions. The earth has experienced such conditions within the past millennium. On the other hand, 4C of cooling would no doubt see substantial glacial advances, dropping sea levels, etc, but it's still well within the climate conditions faced by homo sapiens during their time on earth. An additional 2-4C of warming would result in climate conditions not seen on earth in tens of millions of years.

Haha, I've sometimes called myself a skeptic in that sense (i.e., that it will be worse than let on). Turns out fossil fuel companies have much larger budgets than doomers!

Very rare ultra-Weathergami at Sky Harbor on Sunday. First time a high of 97F and low of 90F was observed at any of the 375 sites analyzed.

Not just Michigan. It's definitely been a very dry month to date in many locations in the lower Great Lakes. Just looking at the data for Fort Wayne, Cleveland and Buffalo, the last time (and only time) it was drier than this year at all three locations was 1936. Fort Wayne, Indiana (5th driest of 128 years) Cleveland, Ohio (11th driest of 155 years) Buffalo, New York (9th driest of 155 years) New Philadelphia, Ohio (2nd driest of 68 years) Bradford, Pennsylvania (6th driest of 65 years) Also, while the official Akron area site hasn't been quite as dry, the site at Akron Municipal Airport [formerly the official observation site for some time] has only registered 0.21" of rain, which is the driest of 83 years at the site.

With that said, I did note a stunning reversal from the high heat and humidity with Saranac Lake plunging all the way to 34F this morning. That reading ties the daily record low set in 1914. The all-time record July monthly record low in the Saranac Lake threaded record is 29F, set on July 8, 1919. At the airport site, the all-time monthly record low is 32F, which has been set on more than one day, last on July 28, 2001. The all-time observed record low for the month of July in the state of New York is 25F, which was set at Allegany State Park, in Cattaragus County, on July 8, 1963.

Also, highly questionable to call the Bay Area likely lived through their coldest summer on record. That's true only if your dataset begins in 2000. Prior to that date, these look like fairly typical temperatures. We can see between 1946 & 1982 (a period of 37 years), there were 19 years as cold or colder than this one at the airport. So this year has actually been above the median summer temperature for the mid to late 20th century. This looks more like typical engagement farming, hype-driven nonsense than an observation predicated on historical data. It's literally just summer. San Francisco Airport San Francisco Downtown

The trend doesn't lie. If anything, this is more like the typical conditions that would have been present when Mark Twain famously quipped that the coldest winter he had ever experienced was a summer in San Francisco. I am assuming the weird anomaly in the 1980s & 1990s is due to a defective HO-83 hygrothermometer installation? I know they had a lot of problems with those reading high.

Wow, in a stunning reversal from the high heat and humidity, Saranac Lake dropped to 34F, tying its daily record low set in 1914. The all-time record July monthly record low in the Saranac Lake threaded record is 29F, set on July 8, 1919. At the airport site, the all-time record low is 32F, which has been set on more than one day, last on July 28, 2001. The all-time observed record low for the month of July in the state of New York is 25F, which was set at Allegany State Park, in Cattaragus County, on July 8, 1963. Edited to remove the reference to Millbrook... I assumed that was a CRN site since xMacis labels it a "WBAN" station and not a "COOP" but it isn't and the temperature data for yesterday appears to be incorrect there. It obviously wasn't 87/32 there yesterday. Lol.

Upper 50s looking likely tonight. Brief cooldown with heat returning on Wednesday. 8” of Reddit rain nowhere to be found.

Wow, that is insane! Is that an 83F dewpoint? Wtf? That is a wet bulb of 85F or 86F, not this WBGT meme, but bona fide wet bulb. A wet bulb of 95F (35C) is deadly if you are out in it for any extended period of time (even inactive and in the shade), maybe even somewhat cooler than that. Definitely take proper precautions in those conditions.

With how much rain there's been of late, I'd say that's a good thing. I hope it continues weakening. Doesn't look like a big rainmaker at this point in any event, although there are still some areas of embedded heavier downpours where I guess a quarter to half inch could fall.

See this kind of rhetoric is unnecessary. The NCEI trend for Southeast Lower Michigan is in close agreement with the Ann Arbor and Detroit data, with the exception that the mean temperature is somewhat below those sites (since the district as a whole is somewhat closer), even without any adjustments for discontinuities (location change) or changes in equipment or time of observations. Maybe a case could be made that the January trend is a little inflated, but all of these sites still show warming in January. And for the annual change, it's quite close to NCEI's numbers. It should be noted that there is NO time of observation bias in the Ann Arbor data - unlike most cooperative observers, they have maintained a consistent evening observation time. Of course, there's none in the Detroit data either (consistent midnight-midnight day, per Weather Bureau standards), but there are a couple of important site changes.

Heck, it aligns almost perfectly with the Detroit threaded record. A touch colder in the early decades, but not surprising considering given the siting/location of the Detroit City record in that era. In recent years, it has shown somewhat less warming, although the broad trends align VERY closely.

I don't CHERRY PICK anything. I also am not opposed to using raw data to show broad trends, but it's important to be mindful of the possible biases in the data being presented. How is noting a bias in the data being biased? As far as any problem with the Ann Arbor data, I'm not seeing it. It's right in line with the rest of southern Michigan for data from the late 1880s - 1890s period, which is freely accessible from NCEI.

I think the biggest surprise for me was how few 70F+ dewpoints there were in 2016 despite that being a scorching summer (hottest on record at Detroit). Only 9 hours at this point at Detroit, and 1 hour at Pittsburgh. Also, somewhat surprising, through yesterday's date, 2016 was 1F cooler than this summer to date at Detroit. It's been 10 years so my memory is getting a little fuzzy, but it must have been an all out torch from here on out that year.

Some PM food for thought:

Saw a post from the Southeast Regional Climate Center about 70F dewpoint hours and decided to take a look in the Great Lakes region, and WOW. Record hours of 70F dewpoints pretty much across the board. Nuts.

The dew lovers must really be liking these trends. Eventually may just be wall to wall 70F dewpoints all summer long?

Here's how Boston is doing for hourly observations with a dewpoint at or above 70F for the season to date: Currently, in 4th place behind 2024, 2013 and 1984, with 188 hours. I wonder how many 70F dewpoint hours have been lost this summer due to some of the ASOS issues? In 2004 & 1951, there were 0 hours with a dewpoint at or above 70F at his point in the season.

Here is Pittsburgh for the summer to date. Wow! Second only to 2005, with 253 hours with a dewpoint at or above 70F so far this season. The average is a hair under 50 hours, although the average is clearly pushed up by anomalously humid years like this one, 2005 & 1949. The median is clearly below the arithmetic mean. By contrast, there were no 70F dewpoints in 1960, 1967, 1975, 1971 or 1976 by this point in the summer. More recently, only 1 hour of 70F+ dewpoints had been observed at this point in 2016 (kind of surprising, as that was a fairly hot summer) and only 3 hours in 2023.

Got this idea from the SERCC X/Twitter account (see post below)