It may not typically snow in D.C. in March (though in my experience that area can be surprisingly wintry through March only to switch to sweltering summer heat after a 3 week spring) but wouldn't significant snow anywhere in the Upper Midwest - which is far from atypical in early March - also have spelled potential doom for his trip due to the likely delays/cancellations at MSP resulting from it?
I think he took a bit of a risk but then it's difficult to blame him for it, Mother Nature can disrupt aviation any time of the year whether it's snow, ice, tornadoes, tropical storms, volcanoes or earthquakes and tsunamis.