Temperatures will plummet across the northeastern United States and are forecast to reach the lowest levels of the season so far during the morning hours this weekend.

As of Friday, the low temperature mark for the season so far is 34 F in Pittsburgh, 42 in Boston, 45 in New York City, 46 in Philadelphia and 48 in Washington, D.C. In some of these cities, temperatures may dip 10 degrees lower than this mark around or shortly after sunrise on Saturday.

The combination of clear skies, diminishing winds and dry air will set the stage for a widespread frost and freeze.

Lows are forecast to be in the lower 20s over the Adirondacks and mountain valleys of northern New England to the upper 20s over the central Appalachians to the lower to middle 30s over many of the suburbs of the major Interstate 95 cities by Saturday morning.

People nursing tender vegetables or fruits may want to consider harvesting them. Bring tender potted plants indoors.

Many areas across the interior Northeast have had a frost or freeze already this season. However, temperatures are likely to be a few degrees lower in the central Appalachians and mid-Atlantic with the cold blast into Saturday morning. This means that some of the suburbs of the major I-95 cities will have their first frost of the season this time.

Temperatures in heavy urban areas of the major I-95 cities should remain above freezing Saturday morning. However, some people who have not yet turned on their heat may need to do so.

People heading out to football games Friday night or tailgating on Saturday should layer their clothing.

Temperatures are forecast to recover to the 50s and 60s across much of the region on Saturday afternoon, thanks to abundant sunshine. Clouds are likely to increase in southern Virginia later in the day.

While a quick temperature drop is likely Saturday evening, some cloud cover should prevent frost in the mid-Atlantic and eastern Great Lakes region Sunday morning.

However, in much of New England, temperatures on Sunday morning may dip to lower levels than that of Saturday morning by a few degrees.

Meanwhile, a tropical or subtropical system will pass close enough to the southern part of the mid-Atlantic region to bring rain and gusty winds Saturday night to Sunday.

A progressive weather pattern, with waves of chilly air and brief warmups typical of late October, is forecast for next week and beyond.