'Sudden summer' in the weather forecast. How hot will it get?

After a chilly start to May, the weather pattern is finally about to flip to summer for much of the Midwest and Northeast over the next few days, forecasters said.

The surge of warmth and humidity is expected to push temperatures into the 80s and near 90 degrees across parts of the Midwest and East, bringing summerlike conditions, according to AccuWeather.

In some areas, including the mid-Atlantic and Southeast, the highest temperatures of the year so far could occur early next week.

However, we aren't switching "permanently" to summer yet, as a cold front is predicted to come through on Wednesday, May 20, reducing the heat for many areas.

How hot will it get?

"For the I-95 cities of Baltimore, New York City, New Haven, Providence, and Boston — unless the heat is able to overcome the onshore flow, which we do not expect — those locations are not necessarily expected to experience a heat wave, with temperatures near the historical average on Monday [May 18]," said AccuWeather senior meteorologist Tyler Roys, in an e-mail to USA TODAY.

However, "going into Tuesday [May 19] and Wednesday [May 20], temperatures will try to shoot into the upper 80s and lower 90s for many of these locations."

Roller-coaster weather pattern

How long will the heat last? Roys said that for many locations — the Ohio Valley, Great Lakes, and into the Northeast and Mid-Atlantic — we will still be in a roller-coaster weather pattern after next week, with some cooler shots likely. "[It will be] nothing like what has been experienced in the latter part of spring, but we do expect something to keep temperatures closer to the historical average, maybe even slightly below," he said.

According to Roys, "for the Plains, while rounds of heat will continue, I would not say the full extent of summer heat is in place. I do expect there to be some breaks in that heat as we move through June."

"For the Great Lakes, Ohio Valley, and into the Northeast and Mid-Atlantic, the point where summer heat truly takes control of the weather pattern will not really arrive until the second half of the summer season," he said.

Humidity will be rising

In addition to temperatures, humidity will also be on the rise over the next few days. “There has been very little humidity during the few warm spells in the Northeast so far this spring, so dew points in the 60s early next week will be quite noticeable,” AccuWeather vice president of forecast operations Dan DePodwin said in an online forecast.

The dew point is the temperature at which air becomes saturated; higher numbers (typically in the 60s and 70s) indicate more noticeable and potentially uncomfortable humidity.

Be wary of the water

While temperatures will be warm over the next several days, the water will still be very cold, experts caution. The National Weather Service in New York warned that "there are cold water safety concerns this weekend as water temperatures remain in the lower 50s. The cold water temperatures can quickly cause hypothermia and physical incapacitation to anyone suddenly immersed in the water."

"Anyone going out on small boats, canoes or kayaks should plan accordingly and use extreme caution to avoid this threat," the weather service said.

Frost mostly done until fall

So are we done with frost advisories and freeze warnings in the East? "We do not necessarily expect any frost for most locations in the Ohio Valley and the valleys of the Northeast and Mid-Atlantic going forward," Roys told USA TODAY. "However, for some higher elevations — specifically northern New England and the upper Great Lakes — that cannot be entirely ruled out yet over the next couple of weeks."

Memorial Day weekend forecast

After the cold front passes midweek, as we head into Memorial Day weekend, the heat will return — at least temperatures will be near to above the historical average for the Ohio Valley and into the Mid-Atlantic, Roys said.

"For the Northeast, however, we have less confidence in above-average temperatures," he said. "The Northeast is considered a transitional area for Memorial Day weekend: some places will likely be above the historical average while others will be closer to what is expected for late May."

Where is a hot summer expected?

A hot summer is predicted across most of the contiguous United States in 2026, with almost no areas expected to have temperatures below the historical average for the season, according to AccuWeather.

The worst of the heat will focus across parts of California, Idaho, Montana, Nevada, Oregon, Utah, Washington and Wyoming, fueling a widespread wildfire threat.

The heat will not be limited to the West. AccuWeather is predicting the number of 90-degree days to be near or above the historical average in Boston, Chicago, New York City and Philadelphia.