Chilly air will push into the mid-Atlantic states around the middle of the week, cutting temperatures back to levels more common of March than late April.
North of the strong temperature contrast zone, it will feel like March, while south of the zone it will feel like June.
"The boundary separating the warm and chilly air will sag southward as the week progresses," according to AccuWeather Chief Meteorologist Elliot Abrams.
Temperatures will fail to climb out of the 40s around Boston on Tuesday and will struggle to climb back into the 50s for the rest of the week. Temperatures will dip to frost levels at night from parts of upstate New York to interior New England by midweek.
"While warmth will hold on farther south in the mid-Atlantic for another day or so, temperatures will be slashed by 10, 20 and even 30 degrees in some areas by Wednesday," Abrams said.
Highs in the 70s and 80s will be replaced with highs mainly in the 50s and 60s during the middle and latter part of the week in the mid-Atlantic states.
Highs will be held to the 40s F in northern New England through Thursday.
Meanwhile, warmth will hold on on the Southeast.
Highs from much of the Carolinas to Florida will be in the 80s to near 90 much of the week. Temperatures will challenge record high levels in some places.
Cool outbreaks like this one are not uncommon well into the spring in New England and the mid-Atlantic states.
Building warmth forces the jet stream farther north over the Central states. Farther east, the jet stream tends to dip southward as a balancing act.
The southward dip can allow arctic air to sag southward in eastern Canada. The chilly air can extend well to the south, where winds turn in off the Atlantic Ocean and low clouds hold on.
Patterns such as this are notorious for producing great temperature differences over a few dozen miles.
As the cool air pushes southward, a couple of storm systems will ride along the temperature boundary. These storms will offer opportunities for rain in parts of the Eastern states, where weeks of dry air and a lack of rain have contributed to an elevated risk for wildfires.