Highs will only be in the 40s across much of the northern tier with lower 50s into places like Atlanta and Memphis.
Some places in New England may not even reach 40 degrees.
Only mid-70s are expected over the next few days as far south as Miami with overnight lows as low as 50 degrees in some outlying areas of the metropolitan area.
Signs of this chilly air mass can be seen in the US map above with numerous frost and freeze advisories and watches in place.
Meanwhile, out west...it is mild and hot. Highs will climb into the 70s and even lower 80s along the Front Range of the Rockies.
In the deserts of Arizona, temperatures will push 100 degrees!
Historically, the last 100-degree day of the year happens around September 28 on average in the Phoenix vicinity.
The latest 100-degree event on record was October 23, 2003.
Here is a neat write-up about the last 100-degree day trend in Phoenix.
Off the teach a CoCoRaHS training class in Brighton, Colorado. Hoping for a good turn-out!