When is it safe to allow swimming after a thunderstorm?

Swimming is considered safe only after waiting at least 30 minutes after the last clap of thunder or flash of lightning. This guideline is rooted in the understanding of how thunderstorms behave and the potential dangers they pose. Thunderstorms can produce dangerous conditions, especially lightning, which can strike bodies of water and pose significant risks to swimmers.

The rationale behind the 30-minute rule is based on the fact that the storm may not be completely over, as additional lightning could occur after the initial storm appears to have passed. The 30-minute countdown should begin after hearing the last thunder or seeing the last lightning strike, ensuring that all danger from the storm has ideally dissipated before returning to the water.

In contrast, simply waiting until the clouds clear or relying on a weather report could lead to assumptions that the danger has passed without adequately accounting for potential lingering risks. Therefore, the safest approach is to follow the 30-minute guideline after the last thunder or lightning before deciding to swim again.