The First Severe Heat of the Year Sweeps Across the Midwest and Northeast

By Alexis George

New Englanders dragged fans and air conditioners out of their closets earlier this week as the first heat wave of the year gripped the Northeast. The hot and humid weather that arrived on Tuesday, June 18th, prompted officials to declare heat alerts as temperatures skyrocketed into the 90s across many locations. And the humidity only made it feel hotter, which caused the heat index to soar over 100 degrees in parts of the Northeast on Tuesday afternoon.

We saw little relief from the hot temperatures on Wednesday as the heat wave continued. Temperatures across New England soared into the mid and upper 90s, with parts of the region posting higher temperatures than South Florida on Wednesday. Boston set a record-high temperature of 98 degrees on Wednesday, which broke the previous record of 96 degrees. A new daily record high of 70 degrees was recorded at Mount Washington Observatory on Wednesday, which broke the previous record of 67 degrees that was originally recorded in 1995. The new record high temperature recorded at Mount Washington on Wednesday also fell a few degrees short of the highest temperature ever recorded in June and the all-time station high of 72 degrees. Here are some other records that were set on Wednesday:

  • Millinocket, Maine, hit 97 degrees, a calendar-day record.
  • Caribou, Maine, hit 96 degrees, matching its all-time high temperature. It also posted a heat index of 103, the highest on record.
  • Bangor and Houlton in Maine tied calendar-day records of 95 degrees.
  • Reading, Pennsylvania, tied a calendar-day record of 95 degrees.
  • Syracuse, New York, tied a calendar-day record of 95 degrees.
  • Poughkeepsie, New York, hit 94 degrees, a calendar-day record.
  • Cleveland tied a calendar-day record of 92 degrees.
  • Buffalo tied a calendar-day record of 90 degrees.
  • Elkins, West Virginia, hit 90 degrees, a calendar-day record.
  • DuBois, Pennsylvania, hit 80 degrees, a calendar-day record.

The heat would not relent on Thursday, June 20th, as heat advisories and excessive heat watches remained in effect for parts of the Northeast. Temperatures were forecast to reach a scorching 99 degrees in Concord, NH, and 95 degrees in Boston on Thursday. The excessive heat also caused some trains in the Northeast to operate at lower speeds on Thursday, as rail temperatures exceeded 135 degrees!

Another daily record high temperature was recorded atop Mount Washington on June 20th, with the new daily record of 65 degrees breaking the previous record of 64 degrees, which was set in 2016 and equaled in 2020.

The high-temperature outlook for the Northeast on Thursday, June 20th.

The heat risk outlook for Thursday, June 20th.

The searing heat felt across the Northeast earlier this week was due to a heat dome, which is a weather phenomenon involving a large and powerful high-pressure system that traps hot air over the region and prevents cool air from entering.

You can learn more about the dynamics of a heat dome, or high-pressure system, and this week’s record heat wave by watching the video of Weather Observer and Education Specialist Francis Tarasiewicz here. Weather Observer and Education Specialist Alex Branton also spoke with New Hampshire Public Radio and The Conway Daily Sun about the new daily record high temperature that was set at Mount Washington on Wednesday, June 19th.

If you are among the millions of people who were in the Northeast this week, you know it has been rough. But it didn’t end there! The hot and humid weather, paired with an approaching cold front, fueled some severe thunderstorms across the Northeast on Thursday. A thunderstorm erupted at Mount Washington Thursday afternoon, which produced several direct lightning strikes at the summit, a sudden temperature drop of 8 degrees, heavy rain showers, and a microburst that caused winds to quickly jump from 18 mph to 91 mph in only ten minutes!

Hays chart depicting the sudden increase in winds caused by a microburst within a thunderstorm

The stubborn heat wave finally died down some by Friday, June 21st, as cooler air arrived behind the passing cold front. While this historic heat wave definitely made headlines in the Midwest and Northeast, on the flip side, a colder weather pattern dumped up to a foot of snow at some higher elevations in Montana and Idaho earlier this week, just days away from the summer solstice!

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