Best time to fly Charleston to Boston

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

Best month

March

81.2% on time · 88 flights

Worst month

September

50.5% on time · 97 flights

Month Flights On time Cancelled When late, by
January 69 81% 8.7% 129 min
February 57 75% 8.77% 67 min
March 88 81.2% 3.41% 84 min
April 113 80.5% 0% 112 min
May 125 79.2% 0% 46 min
June 104 72.5% 1.92% 128 min
July 93 58.9% 3.23% 85 min
August 94 74.2% 1.06% 51 min
September 97 50.5% 0% 53 min
October 99 52.5% 0% 77 min
November 93 77.8% 3.23% 121 min
December 99 74.5% 1.01% 87 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.