Guide
Flying in June: storms, full planes and one airline's bad month
US flights ran 74.3% on time in June 2026, among the worst months of the year. Dallas Love Field fell to 56.5%, and the trouble reached California too.
In June 2026, 74.3% of US domestic flights arrived on time, well below the 77.3% annual rate. Only July and December were worse. One flight in ten arrived an hour or more late, and the month marked the point at which the whole country, not just Texas, moved into its summer shape.
Two things change at once in June. The afternoon thunderstorm season spreads from Texas across the South, the Southeast and the Rocky Mountains. And demand peaks: schools are out, the schedule is one of the heaviest of the year, and aircraft fly full. Storms cause the delays. Full aircraft make every delay harder to recover from, because there is no spare seat on the next flight.
The summer thunderstorm guide explains how convection works on the daily clock and why most of it is filed as air traffic delay rather than weather. This guide looks at which airports and airlines June 2026 actually hurt, and there is one finding that thunderstorms do not explain.
The worst airports in June
US average 74.3%
50.0%90.0%
Source: US DOT Bureau of Transportation Statistics, September 2025 to August 2026.
Across June, 11 of the 60 airports with pages ran below 70% on time. Dallas Love Field finished last at 56.5%, its worst month of the year and one of the lowest monthly figures for any airport in the data. Love Field in June was followed by Houston Hobby in June at 63.6% and Dallas-Fort Worth in June at 63.6%, the latter also cancelling a larger share of its schedule than its annual 2.61%. Chicago Midway, Nashville and Denver filled out the bottom.
Denver is the one that surprises people. Denver in June ran 67.1% on time, its worst month of the year, against 76.6% annually. The mechanism is the mountain version of convection: storms build over the Front Range most summer afternoons and drift onto the plains around the airport, cutting arrival rates just as the evening banks arrive. At Denver in June 2026 only half of departures between 5pm and 8pm left on time, against close to nine in ten in the first window of the morning. The Mountain West guide compares Denver with Salt Lake City, which ran 83.3% in June and barely noticed the season.
Routes out of Dallas-Fort Worth to the leisure markets were among the least punctual in the country. Dallas-Fort Worth to Orlando ran 48.1% on time in June and Dallas-Fort Worth to Tampa 50.2%, flights that can meet the Texas storms on the way out and the Florida ones on arrival. American flies most of DFW's departures, and American at Dallas-Fort Worth ran its weakest months of the year in June, July and August.
MayJune
50.0%90.0%
Figures are on-time percentages. Source: US DOT Bureau of Transportation Statistics, September 2025 to August 2026.
The part the weather does not explain
Look at the chart again. Oakland, San Jose, San Diego and Las Vegas all fell between May and June, the first three by more than five points. Coastal California has almost no summer thunderstorms, and the summer thunderstorm guide rightly lists it as largely exempt. Yet Oakland in June ran 69.7% on time against 78.3% for the year, and San Diego in June 71.1% against 76.3%.
The common factor is the airline. Southwest is the largest carrier at each of those airports, and at Love Field, Hobby, Midway and Nashville too.
US average 74.3%
60.0%85.0%
Source: US DOT Bureau of Transportation Statistics, September 2025 to August 2026.
Southwest ran 66.0% on time across its network in June, the worst of any carrier. At the California airports the gap between Southwest and the other airlines on the same runways was wide: Southwest at San Diego and Southwest at Oakland both ran far below the airports' other carriers in June. More than half of the delay minutes at Oakland, San Jose and San Diego that month were late-arriving aircraft. Almost none of San Diego's delay minutes were charged to weather; the aircraft arriving from elsewhere in the network were, most likely, late.
That is the point-to-point network's weakness in its purest form. Southwest's aircraft fly several legs a day across the country without returning to a hub, so an afternoon storm in Denver becomes an evening delay in Oakland and a late-night one in San Diego. In June the storms hit the airports where Southwest is largest, and the delays spread through the whole network. The data shows the problem followed the airline; it does not show whether anything in Southwest's own operation made it worse that month.
California had a second, separate problem in these months. Flights into San Francisco fell to roughly 35 to 50% on time on several routes from April to July 2026: Las Vegas to San Francisco ran 40.0% in June. The first time I saw those figures I took them for a bug in my own aggregation. Checked against the raw month files, they are in the data.
The data does not say why.
Southwest Airlines75.7% overall
Delta Air Lines81.1% overall
American Airlines74.7% overall
United Airlines78.8% overall
All panels share one scale, 60% to 90% on time. Source: US DOT Bureau of Transportation Statistics, September 2025 to August 2026.
The comparison is stark. Delta led June at 82.3%, and its main hub was one of the best airports in the country that month: Atlanta in June ran 80.1%, above its annual 77.9%, even though Atlanta sits in the heart of the Southeast's thunderstorm belt. Delta at Atlanta had one of its better months of the year. July would be very different. Spirit Airlines does not appear in the June chart: its filings stop in early May 2026, so the data has no Spirit flights in June or July. I have left that gap as it is rather than guess at the reason.
The good end of June
Kahului led at 87.1%, with Honolulu second at 83.7%: the Hawaiian airports' trade-wind weather has no summer season to speak of. San Juan in June ran 83.1%, before the Caribbean storm season starts in earnest. Salt Lake City was the best of the big mainland hubs.
What about holidays?
June has no travel holiday in this site's calendar; Juneteenth on 19 June is not tracked as one. The first holiday of summer is Memorial Day at the end of May, covered in the Memorial Day guide, and the next is the Fourth of July week.
If it were my June ticket
Fly before noon. At Denver, Love Field and Midway the early-evening window ran at or under half on time in June 2026, while the first departures of the day stayed close to nine in ten. Out of Love Field in June I would book nothing later than the first wave. The best time to fly tool shows the pattern for any route.
On Southwest, fly early even in California. In June 2026 the airline's evening flights from Oakland, San Diego and Las Vegas carried delays from storms a thousand miles away.
Connect through Atlanta or Salt Lake City rather than Denver or Dallas if the fare allows. In June 2026 both ran far better, and Salt Lake City's summer figures are consistently strong.
Give connections ninety minutes. One flight in ten arrived an hour or more late in June. The connection risk tool sets the buffer for your specific hub and inbound route.
If the dates can move, move earlier. Nationally May ran 78.6% against June's 74.3%. The data does not reward moving later: July ran 71.7%.
June by airport: Dallas Love Field (DAL) · Denver (DEN) · Houston Hobby (HOU) · Oakland (OAK) · San Diego (SAN) · Atlanta (ATL) · Salt Lake City (SLC) · Compare any US route