Lightning is the fastest way to tell an ordinary rain shower from a storm worth taking seriously. Unlike rain, it can be detected the instant it happens, anywhere in the world, without needing a radar station nearby.
Overview
A lightning tracker maps electrical discharges in near real time. Every flash radiates a burst of radio energy — a “sferic” — which travels enormous distances through the atmosphere. Ground stations record the precise arrival time of that burst, and because radio waves travel at a known speed, comparing arrival times at several stations pins down where the flash occurred.
The technique is called time of arrival multilateration, and it is the same principle satellite navigation uses in reverse. With enough stations, a strike can be located to within a few hundred metres, typically within seconds of it happening.
Why Lightning Detection Covers the Whole World
This is the crucial difference from radar. Rain radar needs a station within roughly 200 km. Lightning sferics propagate for thousands of kilometres, guided between the Earth’s surface and the ionosphere. A relatively sparse network can therefore cover entire continents and oceans.
RainyMap’s live lightning map uses data from Blitzortung, a volunteer-operated network of receiving stations run by enthusiasts and researchers worldwide. It is a genuine example of distributed citizen science producing operational-grade data.
What the Map Shows You
- Individual strikes, plotted as they are detected.
- Recency, usually by colour or fading — the newest strikes stand out and older ones dim.
- Storm cores. A dense cluster marks the electrically active heart of a thunderstorm, which is generally where the heaviest rain, strongest updraughts and any hail are found.
- Storm motion. Watching the cluster over ten minutes shows the direction of travel.
Reading Lightning Alongside Radar
The two together tell you far more than either alone.
- Rain but no lightning — stratiform rain. Wet, possibly prolonged, but not dangerous.
- Rain with scattered lightning — ordinary thunderstorm. Take shelter, avoid open ground.
- Rain with dense, rapidly increasing lightning — a strengthening convective storm. A sharp rise in flash rate often precedes severe weather, including hail and damaging gusts.
- Lightning with little radar echo — possible at long radar range, where the beam overshoots the storm, or in “dry” thunderstorms whose rain evaporates before landing. These are a significant wildfire ignition risk.
Cloud-to-Ground and Intracloud
Most lightning never reaches the ground. Intracloud flashes, which stay within or between clouds, outnumber cloud-to-ground strikes several times over. Detection networks distinguish them, and it is cloud-to-ground activity that matters for personal safety.
Flashes also carry polarity. Most cloud-to-ground strikes are negative. A minority are positive, and those tend to be more energetic, travel further from the parent storm, and are the reason strikes can occur under apparently clear sky several kilometres from the rain.
The 30/30 Rule
A widely used safety guideline: if the gap between a flash and its thunder is 30 seconds or less, the storm is within about 10 km and you should already be indoors. After the last flash, wait 30 minutes before going back out. Sound travels roughly one kilometre every three seconds, so dividing the count by three gives the distance in kilometres.
A lightning tracker complements this rather than replacing it. It tells you where activity is before you can hear anything, but if you can hear thunder at all, you are already close enough to be struck.
Limits Worth Knowing
- Detection is not perfect. Networks miss some flashes, particularly weak intracloud ones and strikes in areas with sparse station coverage.
- There is a small delay. Usually seconds, but do not treat the absence of a plotted strike as proof of safety.
- It is not a warning service. No lightning map issues alerts. For severe weather warnings, follow your national meteorological service.
Frequently Asked Questions
How does a lightning tracker work?
Each lightning flash emits a burst of radio energy that travels thousands of kilometres. Ground stations record the exact time the burst arrives, and comparing arrival times across several stations allows the strike location to be calculated by multilateration, usually within seconds and to within a few hundred metres.
Is lightning detection available worldwide?
Largely, yes. Because radio signals from lightning travel far further than radar can reach, a relatively sparse network covers whole continents and oceans, including regions with no weather radar at all.
How accurate is lightning location?
Within a few hundred metres in areas with dense station coverage, degrading to a few kilometres where stations are sparse. Detection efficiency is higher for cloud-to-ground strikes than for weaker intracloud flashes.
What is the difference between cloud-to-ground and intracloud lightning?
Intracloud lightning stays within or between clouds and is several times more common. Cloud-to-ground lightning reaches the surface and is the type that matters for personal safety. Detection networks distinguish between them.
Can lightning strike when it is not raining where I am?
Yes. Positive cloud-to-ground strikes can travel several kilometres from the parent storm and hit under apparently clear sky. This is why the safety guidance is to go indoors as soon as thunder is audible, not to wait for rain.
How far away is lightning if I hear thunder?
Count the seconds between the flash and the thunder and divide by three for the distance in kilometres. Thirty seconds means roughly ten kilometres, which is close enough that you should already be sheltering.