The main purpose of this ongoing blog will be to track planetary extreme, or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉
Main Topic: More Stats from Climate Change Induced Heatwave Shell
Dear Diary. I like the word enhanced pertaining to heatwaves because in this day and age of the climate crisis all strong episodes can be pegged to our long-term carbon pollution. On a twin Earth that would be cooler without the Industrial Revolution, there would still be heatwaves, but these would not be nearly as numerous or as hot and long lasting as those on our Earth in 2025. And ouch! The further out in time one goes from this point, the worse heatwaves will get…so much so that practically all people around the planet will dread the beginning of the summer season.
I pegged Heatwave Schell as a historic CAT4 heatwave at its peak on Sunday and Monday of this week. That means that it set or tied dozens of all-time records, in this case mostly all-time record high minimums, and as a consequence killed between 500 to 1000 people, which unfortunately it probably did based on reports I am seeing. Mortality stats in association with excessive heat are hard to come by and usually take a week or two to be tallied, so the jury is still out with how many deaths can be pegged in Shell.
Heatwave Shell is not done, though. Its heat dome has collapse, but not entirely. Today I’m pegging the system as a CAT2 looking at the extent of remaining heat advisories:
We will see if the system lingers on into July and makes a comeback over the South.
Here are more details on how hot Shell was in many spots from Yale Climate Communications:
Unprecedented June heat along the Northeast urban corridor, brought to you by climate change
Cities from Philly to Boston break the 100-degree mark, in some cases way ahead of schedule.
by Bob Henson
June 25, 2025
People tried to stay cool in Manhattan and elsewhere on June 23, 2025. On June 24, temperatures approached or exceeded 100°F along the urban corridor from Washington, D.C. to Boston. (Photo by Spencer Platt/Getty Images)
An air mass that had already broken records for early-summer mugginess in the Midwest got even toastier as it pushed into the Northeast on Tuesday, June 24. Millions of Northeasterners ended up suffering through the hottest weather ever experienced this early in summer along much of the Interstate 95 corridor.
The conditions were close to textbook-ideal for such heat across the Northeast and New England, as offshore winds and full sunshine arrived just days after the summer solstice. Farther south in the mid-Atlantic, the heat was more grinding than record-smashing. All told, temperatures on Tuesday approached or topped the 100-degree Fahrenheit mark (37.8 degrees Celsius) all the way from Raleigh, North Carolina, to Manchester, New Hampshire.
It’s no surprise that such conditions could bring unprecedented heat for June in an era of human-caused warming. The Climate Shift Index from nonprofit Climate Central (see Fig. 1 below), which assesses each day’s predicted temperatures against what might be expected if climate change were not present, shows that a widespread area from the eastern Corn Belt to the mid-Atlantic and Upper South was set to experience heat on Tuesday made at least five times more likely by long-term climate change. This area was near the center of a sprawling upper high, a common summer setup that tends to produce prolonged periods of well-above-average heat that are trending hotter as global warming proceeds.
Toward New England, there’s more natural variability in temperatures this time of year, which is likely why the climate-change multiplier was lower there — around two to three. Still, that was enough, combined with the classic heat-making meteorological setup in this region on Tuesday, to produce records that were even more striking than those farther south.
Figure 1. Climate Shift Index for Tuesday, June 24, 2025. (Image credit: Climate Central)
From moist and muggy to miserably hot
The roots of the Northeast’s scorching Tuesday extend back to an exceptionally humid air mass that pushed into the Midwest over the weekend. A few record highs were set, but the richness of the low-level moisture was just as unusual. Undiluted by widespread storms, the muggy air kept many cities incredibly warm for a June night. On Sunday, June 22, Chicago had its earliest 80°F low on record, a level of overnight heat that historically occurred later in summer and only about every five to 10 years or so. Detroit had a low on Sunday of 78°F, also its earliest on record so warm in more than 150 years of record-keeping.
In Minneapolis-St. Paul, the low on Saturday of 80°F was its earliest in records dating back to 1872. The stakes got raised another notch on Sunday with a steamy low of 82°F. The only other times the Twin Cities have ever recorded nights that hot were in 1931 and 1936, during the Dust Bowl, when severe overplowing of the Great Plains helped spark a decade of record-smashing heat — a form of human-induced climate change in itself.
Read: Why were the 1930s so hot in North America?
As the sultry air mass pushed toward the Northeast on Monday and Tuesday – propelled by a moderately strong westerly jet stream – it first ascended the west side of the Appalachians and then descended the east side. As it was forced downslope, the air mass heated even further and the relative humidity dropped, even though the air was still fairly humid. The result: only a few scattered clouds, leaving full late-June sunshine to cook the hot air as it headed toward I-95. The west-northwest flow also kept any chilly onshore breezes from trimming the heat, as they can so easily do in late spring and early summer across the coastal Northeast and New England.
Figure 2. Cloud streaks near the Appalachians show the prevailing west-northwest to east-southeast flow at 3 p.m. EDT on Tuesday, June 24, 2025. The trajectory of the descending low-level air was almost perpendicular to the mountain range, maximizing the warming effect. (Image credit: NOAA Satellites, with YCC annotations added)
Selected stats from Monday and Tuesday’s record Eastern heat
On Monday, New York City’s Central Park had its earliest-ever low of 80°F in data going back to 1869. This was followed on Tuesday by a low of 81°F, making for the hottest pair of consecutive nights ever recorded in Central Park before July 3 in any year. The city also set daily record highs of 96°F on Monday and 99°F on Tuesday, with the latter being only the second time such heat has been recorded in Central Park so early in the year (the earliest 99°F was on May 19, 1962).
Tuesday’s record heat extended into Quebec, where Montreal recorded its second-earliest reading of 35 degrees Celsius (95°F) in any year in data going back to 1872. Tuesday’s Humidex (Canada’s heat index) topped out at 45, tying for the city’s muggiest June day on record. Several Canadian locations set all-time records for June, as noted by Maximiliano Herrera.
Tuesday’s high of 100°F in Raleigh, North Carolina, set a daily record, and both Richmond and Washington, D.C., reached 99°F.
Concord, New Hampshire, broke a daily record of 96°F set way back in 1870 by hitting 100°F on Tuesday (its earliest such reading was 101°F on June 4, 1919).
New York City, New York (Central Park) had its second-earliest 99°F on record (May 19, 1962)
Hottest readings so early in the season set on Tue. 6/24, shown with PORs (periods of record):
- Philadelphia, Pennsylvania: 101°F (old record 102°F on June 29, 1934); POR 1873-
- Newark, New Jersey: 103°F (old record 103°F on June 30, 2021); POR 1931-
- LaGuardia Airport, NYC: 101°F (ties record of June 13, 2017); POR 1939-
Monthly records for June set on Tuesday, June 24:
- JFK Airport, NYC: 102°F (old record 99°F on June 26, 1952); POR 1948-
- Islip, New York: 101°F (old record 96°F on June 19, 1994); POR 1963-
- Providence, Rhode Island: 100°F (old record 98°F on June 15, 1945); POR 1904-
- Manchester, New Hampshire: 102°F (old record 100°F on June 10, 2008; second hottest day on record in Manchester behind 103°F on July 22, 2011); POR 1885-
- Boston, Massachusetts: 102°F (old record 100°F on June 6, 1925); POR 1872-
- Portland, Maine: 99°F (old record 98°F on June 28, 1991); POR 1874-
- Bangor, Maine: 98°F (ties record of 98°F on June 27, 1941); POR 1925-
- All-time any-day heat records set on Monday, June 23:
- Plattsburgh, New York: 101°F (tied with Aug. 1 and 2, 1975 and Aug. 5, 1955); POR
All-time any-day heat records set on Tuesday, June 24:
- Lebanon, New Hampshire: 100°F (old record 99°F on June 18, 1957, and July 20, 1977); POR 1948-
- Augusta, Maine: 100°F (ties record from Aug. 5, 1955); POR 1948-
See below for summaries from Maximiliano Herrera and Don Sutherland of many other noteworthy records set on Tuesday. As always, the preliminary heat records above and below are subject to verification.
Jeff Masters contributed to this post.
Bob Henson
Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance… More by Bob Henson
Bob Henson’s “Unprecedented June heat along the Northeast urban corridor, brought to you by climate change” was first published on Yale Climate Connections, a program of the Yale School of the Environment, available at: http://yaleclimateconnections.org. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.5 license (CC BY-NC-ND 2.5).
Here are more “ET’s” recorded from around the planet the last couple of days, their consequences, and some extreme temperature outlooks, as well as any extreme precipitation reports:
Here is More Climate News from Friday:
(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)