How long should you wait after thunder before going outside?

Start the interval after the last thunder

Record the time of the last rumble of thunder. Wait at least 30 minutes before returning outdoors.

If thunder is heard again, restart the 30-minute interval from that new time.

If lightning is still visible, remain sheltered even if 30 minutes have passed since thunder was last heard. Where a venue, employer, park, pool, school, or emergency authority uses a professional lightning-detection system or a more protective rule, follow its all-clear.

The 30-minute interval is a minimum. A continuing warning, visible lightning, threatening conditions, or an official instruction can require a longer wait.

Remain in lightning-safe shelter

Stay in the substantial enclosed building or enclosed hard-topped vehicle used for shelter.

While inside a building:

• stay away from windows and exterior doors;
• avoid plumbing and corded telephones;
• do not touch equipment connected to an electrical outlet; and
• remain off porches and out of open garages and carports.

Do not move from a safe building to an open pavilion, porch, tent, or vehicle merely because the rain has weakened.

Do not use these as an all-clear

The following do not replace the 30-minute interval:

• rain becoming lighter or stopping;
• brighter sky or a break in the clouds;
• the absence of thunder for only a few minutes;
• the end of a television or phone alert;
• a radar image that appears to show the storm moving away; or
• another person returning outdoors early.

Lightning can remain a threat after the rain ends and after the center of the storm appears to have passed.

For a household or small group

1. Name one person to track the last thunder time.
2. Make the time visible to the group.
3. Reset it whenever anyone hears thunder again.
4. Keep children and pets inside throughout the interval.
5. At 30 minutes, check for visible lightning, current official instructions, and any new thunder before opening the activity.

If anyone is unsure whether thunder was heard, continue the wait and monitor conditions. Do not turn uncertainty into an early all-clear.

For an organized activity

Use the venue's written lightning plan and designated weather monitor. The person responsible for the all-clear should not be occupied with coaching, officiating, performing, or another task that prevents continuous weather monitoring.

Record each reset and announce the all-clear to the whole group. Do not allow different teams or sections of a venue to create competing return times.

Professional lightning-detection systems can support a site-specific plan. A consumer weather app, precipitation map, or historical hazard data is not a professional lightning-detection system.

If thunder cannot be heard reliably

Background noise, hearing differences, an enclosed vehicle, or a large venue may make thunder difficult to hear. Use the responsible authority's lightning-detection plan or all-clear rather than assuming the storm has ended.

If no such system or authority exists and lightning remains visible or conditions remain threatening, stay sheltered.

Do not

• Do not start the interval when rain stops. Start it after the last thunder.
• Do not continue an old countdown after thunder is heard again.
• Do not treat an expired alert as an all-clear.
• Do not leave because another person has gone outside.
• Do not use historical lightning risk or a general weather timeline to declare the immediate area clear.
• Do not shorten a venue, employer, school, or emergency-authority rule that requires a longer wait.

Next action

Write down the time of the last thunder. Restart the 30-minute interval if thunder is heard again. At the end, check for visible lightning and current official instructions before returning outdoors.