Where the lightning data comes from
Boltwatch combines satellite observations and ground-network reports. A dot marks reported lightning, not necessarily a strike on the ground. Different sources cover different places and arrive at different times.
Compare the lightning sources
| Source | Coverage | What is detected | Arrival on Boltwatch |
|---|---|---|---|
| NOAA GOES GLM | Much of the Americas and nearby oceans; limited at high latitudes | Optical flashes inside clouds and towards the ground | Usually about a minute after detection; may take longer |
| EUMETSAT Meteosat LI | Europe, Africa and surrounding waters | Optical lightning flashes, including in-cloud lightning | Ten-minute products, plus delivery and processing time |
| FMI ground network | Nordics and Baltics | Ground-network lightning observations; peak current where available | As reports arrive from the provider; availability varies |
These timings describe Boltwatch’s delivery path, rather than the instrument’s sampling speed. A satellite coordinate is not a confirmed ground-impact location. Read how satellite flashes differ from ground strikes.
Europe, the UK and Africa
EUMETSAT’s Meteosat Third Generation Lightning Imager observes light from lightning over Europe, Africa and surrounding waters. Boltwatch receives reports in ten-minute batches. The batch then takes time to reach the map, so this is a view of recent observations rather than an instant view of every flash.
Satellite observations include flashes inside clouds and flashes towards the ground. They do not label each dot as a ground impact. A location on the map cannot tell you which street, tree or building was hit.
The Nordics and Baltics
The Finnish Meteorological Institute provides ground-network lightning observations across the Nordics and Baltics. These reports may include peak current. Ground sensors estimate lightning locations differently from satellites, so their positions and counts need not match the satellite reports.
The Americas and nearby oceans
NOAA’s GOES Geostationary Lightning Mappers observe lightning over the Americas and adjacent oceans. Reports usually reach Boltwatch about a minute after detection, although delivery can take longer. GOES observations include lightning inside clouds as well as towards the ground.
Read a lightning map alongside weather warnings
Colours show the age of a reported flash. Choose a shorter map time window to focus on more recent dots, or explore the last three hours to see how activity has changed. The nearby panel checks the last 30 minutes within 100 km independently of the map time window. “Near me” measures from your location. A city page measures from the city centre until you choose your own position.
Recent lightning, a thunderstorm forecast and an official weather warning are different kinds of information. The map shows observations. Forecasts estimate future weather. Warnings describe expected hazards and impacts. The distance trend does not predict when a storm will reach you.
An empty map can mean there are no reports in the selected window, reports are delayed, or a source is unavailable. It does not mean it is safe outside. If you hear thunder, go indoors and follow official weather warnings.
Find your country’s map and warning links · How nearby lightning alerts work
Lightning maps and weather radar answer different questions · Estimate distance from thunder
The community station pilot
Boltwatch is also developing an independent receiver network. It is a pilot, not a replacement for established weather services. Joining a station does not prove a location fix, complete coverage or delivery of alerts.