Temperatures along the I-95 corridor are set to drop into the upper 20s and low 30s Friday night into Saturday morning. The National Weather Service has posted freeze warnings from 1 a.m. to 8 a.m. Saturday for Baltimore, Washington and all counties along the Chesapeake from Harford in the north to St. Mary's in the south.

The hard freeze will finally bring the 2009 growing season to a halt in the area, and kill off any tender plants that are still outdoors tonight.

The forecast low for BWI-Marshall Airport - and for much of the surrounding region tonight, is 29 degrees, which would be the lowest reading there since April 13, when the low was also 29. Downtown, the low is likely to be slightly higher, around 33 degrees.

The cold night is brought to us courtesy of high pressure that's been building in from the Ohio Valley. That's bringing clear skies and, as it moves closer tonight, calming winds. And that is the recipe for radiational cooling tonight, which will bleed away much of the solar heating we're able to store up today, and drop temperatures.

The weekend and the early part of next week look like they'll remain mostly sunny during the day, and clear at night. Daytime highs should poke back into the 60s by Sunday.

Then there's this from the NWS:

"HIGH PRESSURE BUILDS BACK IN OVER THE REGION FOR THE END OF
NEXT WEEK. THIS HIGH CENTER SHOULD KEEP ANY MOISTURE ASSOCIATED WITH
ANY REMNANTS OF [tropical storm] IDA WELL SOUTH OF THE CWFA [forecast area] NEXT WEEK."