Temperatures will gradually drop into the 70s tonight before a quick jump back toward the mid-to-upper-80s by the time Thursday’s work day starts.
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But then we’re back to the sweltering heat with temps forecast to settle in the high 90s, peaking at 97. A heat advisory remains in place for most of New England and a heat warning for parts of New Hampshire and Maine. Also an air quality alert has been issued for 11 a.m. to 11 p.m., Thursday for unhealthy ozone levels that could affect sensitive groups, such as children, the elderly and those with lung disease, such as asthma, or heart conditions.
The extreme heat is the result of a heat dome that has stalled over the eastern half of the US, enveloping the Northeast in stifling hot temperatures and humidity. This heat dome is currently centered over the Mid-Atlantic. This massive area of high pressure will continue to funnel in a southerly flow to keep the elevated humidity in place as dew points build to the upper 60s and even low 70s for the Boston area — making for another very muggy day.
“There’s an axis of increasing moisture and increased temperatures, heat that was focused across New England today and starts to move south again tomorrow,” said Bryan Jackson, a meteorologist with the National Weather Service’s Weather Prediction Center.
But relief is in site: By Friday, the high temperatures are forecast to drop into the 80s, just in time for the Celtics victory parade, which starts at 11 a.m.
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The last time the Boston area experienced a heat wave was a six-day stretch from Aug. 4-9, 2022.
PREVIOUS STORY: Air conditioners were in full operation Tuesday and overnight as Boston and much of Southern New England baked under hot and humid air. Logan International Airport reached 92 degrees in the late afternoon with Back Bay, Fenway, and South End temps reaching 95. Logan registered a heat index value of 97 while a weather station at Northeastern University recorded a 102-degree heat index reading.
Wednesday was looking like a near carbon copy — just with a warmer and more humid start as the heat dome settles in for the next 48 hours. Out-the-door temperatures will be in the mid- to upper-70s across the Boston area, a warmer morning that will allow daytime heating to push the thermometer a few degrees hotter than yesterday, reaching the mid-90s. The current record for June 19 is 96 degrees, set in 1923.
Models are backing off ever so slightly from the forecast triple-digit temps for Wednesday and Thursday for the immediate Boston area as a trough over southeast Canada slightly pushes the hot air mass southward. Still, expect a very hot couple of days until relief comes on Friday.
Heat alerts continue to stay in effect today and really through Friday evening with heat index values likely to reach as high as 103 degrees, amplifying heat-related illnesses due to exceptional hot air and high humidity levels.
A handful of heat index values surpassed 110 degrees in Massachusetts on Tuesday, including Bellingham and Chelmsford, with countless other towns and cities seeing heat index values, or ‘feels like’ temperatures, of over 100 degrees across Southern New England.
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Once again, the day should remain mostly sunny with periods of clouds as the day progresses. Classic surface heating may result in a few pop-up showers or thunderstorms that might develop from slivers of convection. Most of the wet weather will be across Northern New England, but any showers should be limited and scattered. Boston should stay hot and dry through the entire day.
The air will feel moderately to very humid with the continued southwesterly flow keeping moisture content high. Dew points will remain mostly in the mid- to upper60s, with a few areas breaking 70. It will feel pretty uncomfortable out so make sure you’re spending limited time outdoors and continue to hydrate.
Wednesday’s breakdown
Southern New England: Very warm temperatures will start the day with morning commute temps in the 70s. Mostly sunny skies with a southwesterly breeze will continue to make it feel muggy. Temperatures will be a bit higher today than yesterday with the same for heat index values. Heat alerts are in place for everywhere except the south coast and southeastern Mass. as a sea breeze will keep it slightly cooler. Temperatures will reach the mid- to upper-90s with heat index values likely to breach 100 degrees for many.
Western Mass.: Excessive heat is in store for the region today with temperatures rising to the mid-90s once again with heat index values between 97 and 105. Alerts remain in place with mostly sunny skies and high humidity making the air feel very humid. The Berkshire hill towns may see a couple of readings at or slightly below 90. A stray afternoon shower may develop but will be brief.
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Cape and Islands: A very similar set-up to yesterday with the Cape being the best place to be today and tomorrow. Temperatures will stay cooler in the upper 70s and low 80s with a cooler breeze from the south. The day should be filled with streaks of sunshine with a few afternoon clouds. It will be slightly muggy across the area with dew points in the low 60s
Northern New England: Excessive heat will sweep through the northern tier of the region with air temperatures reaching the mid-90s with heat index values rising to 100 to 105 degrees. High dew points to the upper 60s will make the day feel really uncomfortable with the risk for heat-related illnesses. There’s the chance for scattered afternoon showers and thunderstorms to develop across Vermont and New Hampshire this afternoon, with a few lingering into Maine.
Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.
