Best time to fly Washington to Philadelphia

Every month pooled across the years on record, so "July" means July generally rather than one particular July. Full DCA to PHL record →

Best month

September

89.5% on time · 232 flights

Worst month

February

56.9% on time · 150 flights

Month Flights On time Cancelled When late, by
January 180 72.3% 7.78% 58 min
February 150 56.9% 8.67% 78 min
March 155 61.4% 1.29% 100 min
April 150 63.8% 0.67% 68 min
May 155 65.3% 3.23% 88 min
June 164 58.9% 7.93% 87 min
July 212 73.3% 8.02% 115 min
August 198 73.8% 3.54% 59 min
September 232 89.5% 0.86% 85 min
October 219 82.6% 0% 49 min
November 169 77.5% 0% 63 min
December 175 63.2% 0.57% 68 min

What a seasonal pattern can and cannot tell you

Months differ for reasons that repeat — summer thunderstorms in the American interior, winter fog and de-icing in northern Europe, school holidays filling every seat and leaving no slack in the schedule. Those are real and they come back each year.

What the pattern cannot do is forecast a particular flight. A quiet month has late days and a bad month has punctual ones. Treat this as a way to choose between two dates you are indifferent about, not as a promise.