A period of rain for several hours moves through from west to east today - attendant to an approaching cold front that will shift our gusty southerly wind to a lighter, cooler, drier northerly wind by evening. With the shift in wind will come a push of drier air, sending rain off to the east of Boston by late day, and off the Cape and Eastern Maine by mid-evening.
As the new air arrives, overnight low temperatures will dip into the 30s, promoting valley fog and some low-altitude clouds near sheltered valleys, but those clouds and fog should burn off Wednesday with enough dry air to bring out the sunshine.
In fact, even with a cool northeast wind that sometimes produces clouds, these next few days will remain bright but cool with daytime highs in the 50s through Friday and overnight lows below freezing for many.
By Saturday and Sunday, shifting wind will allow milder air to arrive, and the weekend should end with highs around 70 degrees!
Marathon Monday may still be mild for the interior, but we're closely watching a "backdoor cold front" - a push of cold air moving at us from the ocean and Atlantic Canada - that may promote cooler temperatures and even a headwind along the race route, to be determined exactly what time that front would arrive Monday. Thereafter, a few days of cooler weather would be likely.