Which days of the year are people flocking to Chicago’s airports? The answer may surprise you.

The Federal Aviation Administration released data on Monday showing the busiest days for arrivals and departures at O’Hare and Midway International Airports over the past year.

If you thought the biggest travel times fell during the holiday season, you’d be sorely mistaken. A majority of the days with the most flights coming in and out of Chicago took place right in the middle of summer.

The FAA analyzed 12 months of data from Oct. 1, 2016, through Sept. 30, 2017, to find that O’Hare saw 11 days with more than 2,700 flight operations.

All of those days fell in the months of June, July or August, with a five-day span between Aug. 7 and Aug. 11 recording 13,526 total flights – an average of 2,705 each day.

The 13 busiest days at O’Hare – plus the number of flights in and out of the airport – were as follows:

Thursday, July 27, 2017: 2,738 operations Thursday, June 29, 2017: 2,733 operations Thursday, Aug. 17, 2017: 2,721 operations Monday, July 31, 2017: 2,716 operations Tuesday, Aug. 1, 2017: 2,713 operations Wednesday, Aug. 9, 2017: 2,712 operations Monday, Aug. 7, 2017: 2,708 operations Wednesday, July 26, 2017: 2,708 operations Tuesday, Aug. 8, 2017: 2,706 operations Friday, Aug. 11, 2017: 2,705 operations Tuesday, July 25, 2017: 2,705 operations Thursday, July 13, 2017: 2,699 operations Thursday, Aug. 10, 2017: 2,695 operations

The data told a similar story at Midway, with one major difference. Midway recorded nine days over the course of that same 12-month period of time with at least 850 flights in and out of the airport.

Like at O’Hare, most of the busiest days at the Southwest Side transportation hub occurred in June, July or August – but the busiest day actually took place in early November.

Those dates, in order, were:

Thursday, Nov. 3, 2016: 904 operations Thursday, June 15, 2017: 884 operations Thursday, June 8, 2017: 872 operations Thursday, July 27, 2017: 872 operations Thursday, Aug. 17, 2017: 863 operations Wednesday, June 7, 2017: 856 operations Tuesday, July 25, 2017: 854 operations Wednesday, Aug 2, 2017: 853 operations Tuesday, May 23, 2017: 850 operations

Three days ranked among the busiest for both Chicago airports, according to the FAA: July 25, July 27 and Aug. 17.