Summer 2025 Starts with Major Heat Wave

The summer solstice was on June 20^th this year, and it didn’t take long for the feeling to set in. For many places around the globe, June 23-26 brought a heat wave that rewrote the record book for early summer temperatures.

In the United States alone, more than 280 locations set new temperature records, and 121 more tied their all-time highs during that span. Most of the new records in the U.S. were set in the northeast. At Davis headquarters in Hayward, California, on the west coast, the high temperature for the 24^th was a comfortable 64 °F (17.8 °C)— a little cooler than usual, actually.

In New York City, however, temperatures in Central Park hit a record-setting 98 °F (36.7 °C) that day, toppling a mark that had stood since the early summer of 1888 and besting the daily average high by more than 16 degrees Fahrenheit. According to NOAA, it was NYC’s hottest day since 2012.

Nearby, in Mill Basin, Brooklyn, a Davis WeatherLink user captured a punishing reading of over 107 °F (41.6 °C).

Boston set a June temperature record for the entire New England region on the 24^th, hitting 102 °F (38.9 °C). Roughly 30 miles northeast, in Lowell, Massachusetts, temperatures reached 99 °F (37.2 °C), breaking the record of 95 °F (35 °C) set in 1957. Even further north, Pinkham Notch, New Hampshire—elevation 2,032ft (619 m)—hit 89 °F (31.7 °C), breaking a record that stood since 1975.

In fact, arguably all the New England states (Connecticut, Rhode Island, Vermont, New Hampshire, Massachusetts, and Maine) experienced or equaled their hottest June days on record in 2025.

It wasn’t just northerners who were treated to the excruciating heat, however. A weather station in Baltimore’s Inner Harbor registered an incredible 104 °F (40 °C), missing the city’s record, which was set in 2012, by a single degree.

At Painted Sky Ranch in Pittsboro, North Carolina, a Vantage Vue user recorded a temperature of 100 °F (37.8 ° C) and a THW index of 134 °F (56.7 °C), indicating the presence of stifling hot winds in addition to high ambient temperatures and humid conditions.

That’s not to say the historic highs only occurred in coastal states. A weather station at a water treatment plant in Springfield, Ohio hit 104 °F (40 °C), breaking their previous high for the date by a staggering 14 °F. A day prior, on June 23^rd, Theilman, Minnesota registered 100 °F (37.8 °C), topping the relatively fresh record of 94 °F (34.4 °C) set in 2023.

In Cape Girardeau, Missouri, cameras captured the road buckling under the pressure of the June 23^rd heat, which reached 92 °F (33.3 °C) with a heat index of 102 °F (38.9 °C), launching an unsuspecting car. About 115 miles away in St. Louis, the same thing happened near the city’s famous Gateway Arch the next day, damaging a major roadway.

Of course, the U.S. wasn’t the only country to feel the heat. In Canada, high temperatures approached records across Ontario and Quebec. In Montreal, June 24^th was the hottest June day on record, hitting 35.6 °C (96 °F) and breaking the previous mark of 35.0 °C (95 °F). In spite of the heat, thousands of Quebecois lined the streets to celebrate the 100^th official public observance of Saint-Jean-Baptiste Day.

In the United Kingdom, the heat coincided with London Climate Action Week, as temperatures around England and Wales reached 34 °C (93 °F). The June temperature record for the U.K. is 35.6 °C (96 °F), and the Met Office believes it could be broken before the month ends.

Six European nations set all-time June records between the 25^th and 26^th: Germany (38.6 °C / 101.5 °F), Poland (38.2 °C / 100.8 °F), the Czech Republic (38.9 °C / 101.3 °F), Luxembourg (36.8 °C / 98 °F), Andorra (37.8 °C / 100 °F), and France (42.3 °C / 108.1 °F). Near the ancient ruins of the Temple of Poseidon in Sounion, Greece, temperatures approached 40 °C (104 °F), making it even tougher to fight the nearby wildfires.

On the 26^th, relief arrived across the northeast U.S., with a “backdoor” cold front that dropped temperatures as much as 25 degrees Fahrenheit day-over day throughout the region.

This map was captured at 12:00PM Eastern on 6/26/2025 and represents temperature deviations compared to 24 hours prior. Some temperatures dropped as much as 25 degrees in one day.

That same day, however, the heat wave moved eastward into the Balkans, triggering temperatures as high as 41 °C (106 °F). Even as North America and western Europe get some relief, a second round of hot days appears to be in store for both continents as June transitions into July.

This kind of recordkeeping is only possible because of businesses, communities, research teams, and individual citizens around the globe who maintain properly sited weather stations and share that data publicly. If you’ve got a Davis weather station, you could be contributing to the dialogue and record books by participating in the WeatherLink community. If you don’t have a weather station yet, we can help you find one that matches your goals and budget.