DATA PROVENANCE / PUBLIC

Lightning Tracker Data Sources & Methodology

Lightning Tracker combines NOAA GOES-19 East and GOES-18 West GLM optical-flash feeds for supported portions of United States and Canada maps, and EUMETSAT MTG-I1 LI for the United Kingdom map. Fixed source boundaries prevent overlapping satellite observations from being counted twice.

For what an optical-flash marker can and cannot locate, read how accurate lightning maps are. For counts and rates outside this live detection window, read US lightning statistics.

Last updated Methodology v1.1 · clarified source identities and fixed boundaries Public maps: US · Canada · UK
01 / SOURCE MATRIX

Where Each Signal Comes From

Each layer answers a different question. Lightning detections are not precipitation radar, and neither replaces an official warning.

G19 + G18 NOAA GLM

GOES-19 East + GOES-18 West

NOAA's Geostationary Lightning Mapper instruments detect optical lightning flashes from orbit. Lightning Tracker assigns East and West observations to deterministic longitude bands, split at a -106.1° longitude, so their overlapping views do not produce duplicate flashes in the shared pipeline. This uses NOAA product GLM-L2-LCFA.

Server poll: 30 seconds GLM processing: full to 52°N; edge to 55°N
Official NOAA NESDIS GLM documentation →
MTG-I1 EUMETSAT LI

Meteosat Lightning Imager

EUMETSAT MTG-I1 Lightning Imager supplies recent optical flashes for the United Kingdom regional map and supports European coverage. A second fixed longitude boundary separates its Atlantic overlap from GOES East processing at -37.5° longitude. The UK public route is capped at that boundary. EUMETSAT collection: EO:EUM:DAT:0691.

Server poll: 60 seconds Public use: UK pilot
Official EUMETSAT MTG LI documentation →

Contains modified EUMETSAT Meteosat data © EUMETSAT 2026.

SPC FORECAST

NOAA Storm Prediction Center

SPC convective outlooks provide categorical and probabilistic storm-risk context for days 1 through 8. They are forecasts, not live lightning detections, and remain visibly separate from map markers and nearby-strike results.

Layer: forecast context
Official NOAA SPC outlooks →
RADAR PRECIPITATION

Current Released App Radar Layer

The currently released mobile app can display RainViewer precipitation-radar frames for rain and storm-structure context. Radar providers may change between app releases; the current app and its About screen are the source of truth for the provider active in an installed version. Radar does not directly detect lightning.

Layer: precipitation radar
RainViewer source information →
02 / EVENT MODEL

What Lightning Tracker Stores

GLM events are illuminated pixels in a 2 ms frame. Adjacent simultaneous events form groups; groups within less than 330 ms and 16.5 km form flashes. Group and flash locations are radiance-weighted centroids, not surveyed ground-impact points.

Deduplication is deterministic: stable provider event IDs use a shared source + provider_event_id identity, and fixed disjoint longitude bands prevent cross-satellite overlap. These rules remove duplicate pipeline records; they do not create a latency guarantee.

03 / TIMING

Poll Cadence Is Not Display Latency

Three clocks affect what appears on screen. A fixed poll interval never guarantees an identical end-to-end delay.

  1. 01

    Provider publication

    Satellite processors publish products after observation. Availability varies with source processing and network conditions.

  2. 02

    Server polling

    Lightning Tracker checks GLM feeds every 30 seconds and MTG LI every 60 seconds, then parses and stores new flashes.

  3. 03

    Shared processing

    Source filtering, deterministic overlap handling, persistence, clustering, and API delivery add variable processing time.

  4. 04

    Browser refresh

    Public interactive maps request fresh data every 90 seconds while open. A browser can therefore update later than the server poll.

Practical meaning: GLM 30 seconds, MTG LI 60 seconds, and browser 90 seconds are cadences—not promises that every observation appears within that exact time.

04 / BOUNDARIES

Coverage and Safety Limits

OPTICAL SIGNAL

A flash marker is not always a ground strike

GLM and LI observe optical lightning flashes, including substantial intra-cloud activity. Do not interpret every marker as a classified cloud-to-ground strike.

NO ALL-CLEAR

An empty map does not prove safety

Satellite visibility, source processing, network delivery, and refresh timing can delay or miss detections. If you hear thunder, move indoors.

PUBLIC MAP SCOPE

Routes do not equal sensor coverage

Public routes exist for the United States, Canada, and the United Kingdom. The GLM pipeline treats coverage as full only through 52°N and as edge coverage from 52°N through 55°N. Alaska and Canadian locations north of 55°N are outside the configured GLM footprint and may return no provider. The UK route uses MTG-I1 LI. Route availability never proves complete detection or all-clear.

OFFICIAL GUIDANCE

Not an emergency warning service

Use local meteorological agencies and emergency authorities for official warnings. Lightning Tracker adds situational context; it does not replace them.

Open US lightning maps Open Canada map Open UK map Embed US state lightning data