Thunderstorm risk at outdoor events
Summer storms are a known risk for festivals, shows and open air stages. This guide sets out what PLASA's Lightning Guidance for Outdoor Events asks organisers to plan for.
Plan before the storm
PLASA says lightning storms in the UK summer are reasonably foreseeable. It says the threat should be part of the event risk assessment with a clear and proportionate response plan if storms are forecast.
The plan should cover production and event staff as well as visitors. It should fit each phase of site activity, including the build.
Source: PLASA: Lightning Guidance for Outdoor Events, 1st edition, June 2019
Time to safety
PLASA says the longer it takes people to reach safety, the earlier the organiser needs to decide to cancel, suspend or evacuate. For larger or high risk events that decision may be needed hours ahead, so reliable forecasting is fundamental.
It warns that simply stating all temporary structures will be evacuated is unhelpful if there is nowhere safe to send people. Marquees and stages may give a degree of protection if they are well built and earthed. They are almost certainly better than sheltering under trees.
Source: PLASA: Lightning Guidance for Outdoor Events, 1st edition, June 2019
Distances on the day
As an example for a large event, PLASA describes three steps. With a storm in the area, alert all staff. With lightning detected at 10km and closing, about 30 seconds from flash to bang, bring staff down from high workplaces and towers. At 6km, about 18 seconds, stop the show and evacuate.
Its 30:30 rule says a gap under 30 seconds between flash and bang means danger. Wait 30 minutes after the last such strike before carrying on.
Source: PLASA: Lightning Guidance for Outdoor Events, 1st edition, June 2019
Forecasts and detection
PLASA says there must be a reliable means of monitoring the weather. For some events that means close attention to services such as the Met Office. For others it means professional services and detection technology.
A forecast chance of thunderstorms is the prompt to brief staff and check the plan. It cannot tell you where lightning is striking on the day.
Source: PLASA: Lightning Guidance for Outdoor Events, 1st edition, June 2019
How Gustline helps
Gustline's thunderstorm risk alert is a forecast, not live lightning detection. It warns when the Met Office forecast chance of thunderstorms at your site reaches your threshold. The default of 20% is a Gustline starting point, not a published figure. Gustline does not detect strikes, so use your own monitoring on the day.
Gustline checks the Met Office site-specific forecast for the point you pin on the map, every six hours from a week out and every hour in the final three days. It compares the forecast gust with the rated limit you enter for each structure and checks the weather alerts you leave on for the event. When a level changes it emails and texts the people you choose. Every alert is logged with a timestamp.
Gustline is an early warning for planning. It does not replace checks on site on the day, the official warnings or your event's own plans.
Plans start at £19 for one event. A season pass is £99 a season and a year pass is £179 a year. It covers the UK only.
Set up alerts for your next eventSources
Last updated 4 October 2026.
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