Best time to fly Washington to New York

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

Best month

April

86.2% on time · 29 flights

Worst month

June

57.8% on time · 119 flights

Month Flights On time Cancelled When late, by
January 123 84.3% 6.5% 63 min
February 102 75% 5.88% 80 min
March 116 66.7% 11.21% 72 min
April 29 86.2% 0% 45 min
May 138 74.1% 2.17% 43 min
June 119 57.8% 8.4% 89 min
July 167 64.5% 8.38% 61 min
August 231 72.8% 7.79% 78 min
September 216 83% 1.85% 53 min
October 222 80.5% 0.45% 61 min
November 207 68% 6.28% 53 min
December 230 71% 2.61% 71 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.