Much to the chagrin of Punxsutawney Phil, spring has just about sprung across the eastern U.S. Milder than average temperatures are set to spread over many of the eastern states next week amid a large-scale weather pattern change.

Before next week is done, 60-degree temperatures are possible as far north as southern New England, with a chance the Mid-Atlantic could make a run at 70 degrees.

The upcoming pattern shift is a gradual transition to a more springlike weather regime, in which mild temperatures and an uptick in severe weather in parts of the country are likely.

Here’s how the transition will likely play out:

Temperatures on Wednesday were in the upper 30s to low 40s in Boston during the afternoon and sat in the upper 50s in the nation’s capital. New York City was near 50, while Atlanta enjoyed temperatures in the mid to upper 60s.

Cold air will remain entrenched in the Northeast in the coming days, keeping Boston and most of New England in the 30s until early next week. The Mid-Atlantic will lie within the transition zone of cool air to the north and warmth building to the south. After a mild midweek period, D.C. will spend Friday and the weekend in the 40s — cooler than average for the date. Washington, D.C.’s highs in early March are more typically in the lower 50s.

That cool air mass will hang around along and east of the Appalachians through Sunday before retreating north. At the same time, strong high pressure passing offshore of the Carolinas will induce a broad southwesterly flow of air, allowing warm air to spread up the East Coast and the Mississippi, Tennessee and Ohio Valleys.

Then on Monday, temperatures will warm 5 to 10 degrees above average for most of the eastern United States and up to 20 degrees above seasonal levels across the north central Plains.

Minneapolis could hit 50 on Monday for the first time since Dec. 9, while temperatures in the upper 60s to near 70 may spread over most of Kansas and Oklahoma. Texas and other Gulf Coastal states will see temperatures soaring well into the 70s, and even Chicago could flirt with the 60-degree mark. Washington, D.C. will likely clip 60 as well, as may Atlanta and Charlotte.

Monday night’s lows may even approach record mild territory in the northern Plains and Corn Belt. Omaha could see a record high minimum set early Tuesday — the predicted morning low of 47 beats out its previous record warm low of 46 degrees set in 1902. It also matches the city’s average high for the date, highlighting just how mild overnight temperatures may be.

That should give many cities a head start on next Tuesday’s temperatures. In the East, that warmth will begin to take hold and surge north, allowing cities such as D.C. and Baltimore to leap well into the 60s, with the mid-to-upper 50s possible in New York City.

Chicago will enjoy a high near or above 60 for the first time this year. Chicago hasn’t made it above 52 degrees so far in 2021; the Windy City’s average date for the first 60 degree reading of a year is Feb. 25.

There are signals that next Wednesday could be even warmer on the Eastern Seaboard, with mid 60s possible in the Mid-Atlantic and a chance even Boston could hit 60 degrees.

By mid-to-late next week, daily weather details remain hazy, but there are signs of a developing low pressure system to the west that could bring inclement weather as it progresses east. Southerly and southwesterly winds ahead of the approaching frontal system would induce the transport of mild, moisture-rich air up the East Coast.

There is the potential that the front may trigger strong to locally severe thunderstorms in parts of the central and southeastern United States, but confidence in any specific details remains low so far in advance.

Behind the front late next week, a brief cool-down is possible, though the extended-range forecasts continue to point toward above-average temperatures for much of the eastern half of the nation. The National Weather Service’s Climate Prediction Center has highlighted the odds of above-average temperatures, particularly east of the Mississippi, for much of the next two weeks and beyond.