Sept. 1 marks the beginning of meteorological fall, which runs until Nov. 30, and a chilly airmass will be ushered in across the East and South along with the change in season.

A southward dip in the jet stream, or upper-level trough, was the common weather pattern during the summer in the East, while a northward bulge in the jet stream, or upper-level ridge, often set up in the West. This overall pattern looks to continue through the first week of September and possibly beyond.

Temperatures are typically below average underneath a trough as cooler air is drawn southward out of Canada, and a blast of true fall-like air will engulf the eastern and southern states at times during the next several days.

Late Week into This Weekend

A cold front swept through parts of the Midwest and Northeast on Thursday, and now some of the coolest temperatures since last spring will be possible into Saturday in some locations. Temperatures are expected to be 10 to 25 degrees below average in a broad swath from the Mississippi Valley to the mid-Atlantic and Northeast.

(MORE: Labor Day Weekend Forecast)

In fact, several record lows have already been set. On Friday morning, record lows were set in Alpena, Michigan (36 degrees – tied); Watertown, New York (37 degrees – tied); Flint, Michigan (39 degrees); Binghamton, New York (42 degrees); Syracuse, New York (42 degrees – tied); Poughkeepsie, New York (43 degrees) and Bridgeport, Connecticut (52 degrees – tied).

On Saturday morning additional record lows were broken, including, Glens Falls, New York (34 degrees); Albany (38 degrees); Binghamton, New York (39 degrees – tied); Poughkeepsie (40 degrees); Hartford, Connecticut (41 degrees); Providence, Rhode Island (46 degrees); Newark, New Jersey (49 degrees) and New York City’s LaGuardia Airport (56 degrees – tied).

Frost advisories were even issued in some spots Friday and Saturday morning, where some patchy frost was observed.

(MAPS: Average Monthly Temperatures)

Forecast Highs

A few record-cold high temperatures have also been observed. On Friday the following cities set new records for coolest high temperature for the date: Dayton, Ohio (59 degrees), Columbus, Ohio (62 degrees), Pittsburgh (63 degrees) and Watertown, New York (64 degrees).

Many places will likely get stuck in the 60s for highs Saturday, so it may be time to dig out your light jacket or sweatshirt, even if you are outside during the warmest time of the afternoon. A few spots in northern New England may even be stuck in the 60s into Sunday afternoon.

Several locations in the mid-Atlantic could threaten record-cold highs Saturday afternoon, including Philadelphia and Baltimore.

Next Week

Temperatures will return closer to average early next week before another cold front sweeps through much of the East and South Tuesday into Wednesday.

(MAPS: 10-Day Forecast High/Low Temperatures)

Forecast Highs Next Week

This next cool shot doesn’t look to be quite as chilly as this weekend’s, with temperatures expected to be generally 5 to 15 degrees below average mid- to late next week.

This means highs will be in the 60s and 70s across the Northeast, mid-Atlantic, Midwest and even much of the South. However, temperatures may get stuck in the 50s across the upper Great Lakes mid-next week.

Lows should dip into the 50s as far south as the mid-South region mid- to late next week. In the upper Mississippi Valley and upper Great Lakes, a few spots may fall into the 30s and 40s. The Southeast and Gulf Coast will likely hold in the 60s to near 70 degrees for lows.