You could feel the fresh fall-like air whizzing into the region this afternoon as winds from the northwest gusted up to 30 mph.

D.C.’s afternoon temperatures in the mid-80s were just a few degrees below average, but to our northwest some locations were 20 degrees cooler than normal.

High temperature departures compared to normal today, as forecast by the GFS. (

As the core of the cool air oozes east, air temperatures will be 8-15 degrees below average through much of the Mid-Atlantic and Northeast by Tuesday morning.

Low temperature departures compared to normal tonight, as forecast by the GFS. (

A snapshot from the hi-res NAM shows the details of  how cool it expects temperatures to get this by early Tuesday morning (6 a.m.):

High resolution NAM model forecast temperatures at 6 a.m. Click to enlarge. (


And look at Tuesday afternoon…

High resolution NAM model high temperature forecast for Tuesday. Click to enlarge (

Highs in the upper 70s in D.C.? That’s what we expect in mid-to-late September. For perspective, it was 104 three years ago on July 29 (2011).  If you’re headed to the high peaks of West Virginia, highs will be stuck in the 60s after lows in the 40s.  Veritable sweater weather!

As an added bonus, humidity levels are going to be way low.  Dew points will drop into the upper 40s to low 50s late Tuesday into Wednesday.  For reference, anything below 60 indicates low humidity and extremely refreshing conditions at this time of year.

Dew point forecast at 2 a.m. Wednesday morning from GFS Model (

After Wednesday morning, the relative “cool” relaxes, but the European model still boasts cooler than normal mornings (blue shades) through the weekend for much of the eastern U.S.

Temperature difference from normal at 8 a.m. Tuesday through Sunday from European model (

Capital Weather Gang’s Ian Livingston contributed to this post.