Best time to fly Bloomington/Normal to Chicago

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

Best month

August

93.3% on time · 62 flights

Worst month

December

63.6% on time · 79 flights

Month Flights On time Cancelled When late, by
January 58 84.2% 1.72% 184 min
February 72 91.7% 0% 61 min
March 93 76.1% 5.38% 142 min
April 144 83.9% 0.69% 83 min
May 181 92.3% 0% 64 min
June 127 81.3% 3.15% 66 min
July 62 75.4% 1.61% 72 min
August 62 93.3% 3.23% 45 min
September 60 85% 0% 87 min
October 61 75.4% 0% 52 min
November 86 82.7% 12.79% 84 min
December 79 63.6% 2.53% 89 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.