Why summer heat is more likely to ground your flight than cold weather

The summer travel season got a rocky start in late June when thunderstorms, coupled with airport staff shortages across the US, caused as many as 7,700 flight delays and 2,200 cancellations in a single day.

But a lightning strike isn’t the most likely way travel plans get snarled. Passengers are learning the hard way this summer that high temperatures can be as disruptive to on-time departures as visibly inclement weather.

This week extreme heat has rippled across much of the US and Europe. Cities experiencing record-breaking temperatures have included Miami; Tampa; Portland, Oregon; San Antonio; and New Orleans. In Phoenix, July 12 marked the area’s 12th consecutive day of temperatures reaching over 110 degrees. The heat wave is said to have affected a quarter of the American population.