Best time to fly Phoenix to St. Louis

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

Best month

February

84.9% on time · 192 flights

Worst month

June

67.7% on time · 166 flights

Month Flights On time Cancelled When late, by
January 199 83.8% 1.01% 44 min
February 192 84.9% 0% 37 min
March 234 73.4% 0% 69 min
April 207 75.9% 0% 46 min
May 202 77.9% 0% 46 min
June 166 67.7% 0.6% 53 min
July 166 77.9% 0.6% 48 min
August 164 78.5% 0.61% 53 min
September 159 82.8% 1.26% 54 min
October 199 80.9% 0% 78 min
November 189 75.4% 0.53% 50 min
December 207 75.4% 0% 60 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.