After a very warm first half of October in the eastern half of the nation, increasingly chilly blasts of air for the second half of the month will be a reminder that winter is on the way.
The crispness to the air that is typically felt as the days grow shorter has been absent thus far in October for many locations east of the Mississippi River.
Pushes of Canadian air are forecast to grow more frequent as the end of the month approaches, bringing more typical and, in some places, significantly colder conditions.
The most noticeable cooldown will be felt west of the Appalachians where the core of the Canadian air will drill southward.
AccuWeather.com Expert Senior Meteorologist Alex Sosnowski details the first shot of cold air entering the Upper Midwest and Great Lakes this weekend. The first snowflakes of the season can fly in these areas; however, a major snowfall is not anticipated.
Along the mid-Atlantic and New England coasts, the cool air will have more trouble establishing itself.
After a bit of wet weather to end the week, residents of the I-95 cities will notice cooler conditions later in the weekend with the chilliest weather early next week although daytime highs will still be mainly in the 60s.
A heavier jacket will be needed during the morning hours early next week from Philadelphia to Boston.
"While the pattern will bring the coldest air of the season so far in terms of daytime highs from the Midwest to New England and the mid-Atlantic, it does not favor snow for the I-95 corridor," Sosnowski said.
A second push of Canadian air is expected to ratchet temperatures down another notch by later next week. Once again, the sharpest downturn in temperatures will be found in the Ohio and Tennessee valleys, where a hard freeze or heavy frost is likely late next week.
AccuWeather.com Expert Senior Meteorologist Dale Mohler noted, "This will be relatively late for a hard freeze in most places and should not cause much in the way of crop losses."
A series of weather events thousands of miles away is partly responsible for this cool spell. In the Western Pacific, typhoons that curve east of mainland Asia typically help change steering winds in the eastern U.S. six to 10 days in the future, leading to below-normal temperatures.
This rule of thumb will be on display with the cold blast forecast for late next week.
AccuWeather.com Long Range Weather Expert Paul Pastelok explained, "With Typhoon Wipha recurving by Japan on the 16th, steering winds will drop southward over the eastern U.S. and lead to cooler-than-normal weather around the 24th of the month."
If additional typhoons recurve before striking mainland Asia through the end of October, it could add more fuel for additional waves of chilly air in the Midwest and part of the Northeast.
A return to average to below-average temperatures is in sharp contrast to the start of the month where most places from New York City to Chicago were much warmer than average.
This is also a noticeable departure from last year where the first 15 days of October were at or cooler than average.