Yesterday's highly-anticipated launch of a Falcon 9 rocket that will carry a Dragon capsule with astronauts Robert Behnken and Douglas Hurley to the International Space Station, was scrubbed with 17 minutes left in the countdown because of the danger of lightning. While there were no thunderstorms in the immediate vicinity of Launch Complex 39A at Cape Canaveral, there was concern that the electrostatic charge in the atmosphere was high enough were the Falcon 9 rocket could have triggered lightning as it passed through the atmosphere.
SpaceX will try again to launch the Falcon 9 on Saturday afternoon with the launch window opening up at 3:22 PM Eastern Time. There is a 40 percent chance of Saturday's launch being scrubbed again for a weather violation.
This brings home the point that weather is a major challenge for launching a space mission from Florida from late spring, through summer, and into the early autumn. Being surrounded on three sides by warm, tropical waters means there is abundant moisture and a relatively unstable air mass in place over Florida during this time. Differential heating between the land and adjacent water contributes to sea breeze fronts that create a focal point for thunderstorm formation during the afternoon. Unfortunately the Falcon 9 launch window falls right around the time that diurnal thunderstorms typically start firing along the Florida coast as the sea breeze front works its way inland and lifts the moist, unstable air air mass.
Even though any thunderstorms are many miles away, the concern about electrostatic charge in the atmosphere is always a concern. The U.S. Space Force's 45th Weather Squadron at Cape Canaveral Air Force Station has an extensive network of weather radars, lightning detectors, electric field mills, wind profilers, and ground-based weather stations to detect conditions that would result in a weather violation. A weather violation would be any atmospheric condition that falls outside the criteria required for a safe launch. Accordingly, the launch is scrubbed, or in other words, postponed until the next available launch window should a weather violation occur. This process repeats itself for every launch attempt until weather conditions allow for the Falcon 9 to lift off.
If you don't succeed the first time, try, try again.