Behind the Forecast: How weather impacts Thunder Over Louisville

LOUISVILLE, Ky. (WAVE) - Thunder Over Louisville is the official kickoff to the Kentucky Derby Festival. Out of the 30 full Thunder Over Louisville shows we’ve had since 1990, rain has fallen at some point in the day for half of them. Weather is vital to the show overall, and organizers have specific criteria when planning the air and fireworks shows. We’ve seen everything from sleet falling to 82° and sunshine for Thunder.

Rain usually doesn’t affect the aircraft; those watching the airshow are more impacted by rainfall. If a thunderstorm is nearby, a “no-fly” may be issued. Once the thunderstorm is gone, the show can continue.

Clouds on their own can impact the air show. The air show is required to have a ceiling height of 1000 feet. Ceiling height is the height of the ceiling in feet above ground level (AGL), defined as the lowest broken or overcast cloud deck observed, according to the National Weather Service. When clouds are under 3000 feet, only acts that have a “low” show can perform and no vertical maneuvers are allowed.

When the wind reaches more than 23 MPH, it limits what planes can do during the air show. The wind near the Ohio River is vital to planning, but so is the wind speed at the Louisville Muhammad Ali International Aiport. Some of the fastest aircraft in the show use the airport’s longest runway. If the winds are too strong, then longer runaways may be unavailable, grounding some planes. Thunder Over Louisville organizers say that winds over 28 MPH will ground all sky-diving teams.

Rain does not usually delay the fireworks show unless a downpour is expected at the launch time. Severe thunderstorms or tornado warnings will also delay the show. Wind over 23 MPH can distort fireworks patterns. Thunder officials analyze wind speed at launch time to see if a delay is necessary.

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