Residents of the northeastern and midwestern United States should not get use to the September-like air pouring in early this week.
Low humidity and temperatures more representative of September will continue to filter across the Great Lakes, Ohio Valley, Northeast and mid-Atlantic through the first half of this week.
Comfortable conditions will also seep well into the Deep South for a time.
“The only real difference in how it will feel compared to September will be the strong June sunshine,” AccuWeather Senior Meteorologist Alex Sosnowski said. “Where and when the sun is out, it will feel warm, especially in your car.”
Do not assume that the cooler air will lessen the risk of getting a sunburn. Even when temperatures are stuck in the 60s, the sun’s rays as just as strong as when highs in the 80s and 90s are expected.
Spotty showers and thunderstorms will prevent bright sunshine from complementing the comfortable air in parts of the Midwest and Northeast. Waterspouts may even spin up over the Great Lakes, as well as small hail.
More violent thunderstorms will threaten the western Great Lakes at midweek as the summer heat and humidity begins to make a comeback.
“After a pleasant start to the week with low humidity and below normal temperatures, we expect a pattern change late this week in the central and eastern United States,” AccuWeather Long-Range Meteorologist Max Vido said.
As the high pressure responsible for the September-like air shifts offshore, the door will open for warmer and more humid air to surge northward.
Humidity will build across the Great Lakes from west to east Wednesday into Thursday.
The I-95 corridor of the Northeast will experience a noticeable rise in temperatures on Thursday. However, the arrival of sweltering humidity is likely to be delayed until Friday and will not be quick to depart.
“The I-95 corridor can expect several days of temperatures in the upper 80s to low 90s late this week into the early part of next week,” Vido said.
While the region has dealt with such sizzling temperatures so far this summer, it will be quite a change compared to Tuesday's expected highs of the middle and upper 70s from Washington, D.C., to New York City to Boston.
When humidity is factored in, the change will be even more noticeable.
“High humidity will send AccuWeather RealFeel® Temperatures well into the 90s, so residents will need to stay properly hydrated when going to outdoor activities and Independence Day cookouts," Vido said.
Temperatures are likely to not soar as much as humidity levels in the Midwest and interior Northeast late this week and through the holiday weekend due to more clouds and thunderstorms, according to Vido.
However, humidity will still make the air uncomfortable and have residents turning up air conditioners and fans.
“While the more active weather is expected farther inland, thunderstorms could push to the Northeast coast on several days, providing some relief to the uncomfortable afternoon heat,” Vido said.
Any more persistent heat relief is likely not in the offing for the Northeast beyond the holiday weekend.
“After the Fourth of July, we could be heading into a warmer pattern for the mid-Atlantic and southern New England as the Bermuda High strengthens,” he said.
The Bermuda High is a semi-permanent area of high pressure situated over the central Atlantic Ocean and is notorious for pumping heat and humidity across the Eastern Seaboard when it builds westward.