Lightning in the Virgin Islands

How much lightning did the Virgin Islands get in the past year?

GOES-19 recorded 61,386 lightning flashes over the Virgin Islands and the sea around them between October 8, 2025 and October 7, 2026, on 177 of the 365 days. The busiest day was October 17, 2025, with 12,920 flashes, as a stalled front met deep tropical moisture. October 2025 (from the 8th) had the most (33,467); January 2026 the fewest (80).

The frame: 17.3–19.2° N, 65.95–63.85° W, Culebra and Vieques to Anegada and St. Croix (about 222 × 210 km). Every flash GOES-19 GLM L2 Full Validation, Product Performance Guide (NOAA OSPO, 2026) recorded with a good quality flag; 3.9% more carried a degraded flag and are left out.

Lightning by island

Lightning within 10 km of each island's shore in the past year. Tortola had lightning that close on the most days, 35; St. Thomas on 29.

“Within 10 km” is a flash whose centre fell over the island or within 10 km of its shore; GLM’s pixels are about 8 km across, so a flash “over” a small island is a flash in the cloud above it, not a strike on it.

When lightning season is

The year followed the islands' wet season. October 2025 was the stormiest month, with 33,467 flashes from the 8th on; the dry months from November to March had 1,070 between them. April flared with an upper-level trough (7,429 flashes, most on the 13th and 14th), and the lightning built again from August. Ship reports off the Virgin Islands in NOAA's Coast Pilot agree: thunder and lightning in 4.3% of observations in September and 4.4% in October, against 0.1% from January to April. The wettest months are September to November.

What time of day storms come

Over land, the afternoon belongs to the storms: Puerto Rico's flashes peak around 2 PM, and 95% of them come between noon and 7 PM, after the sun has heated the island and its mountains. Over the sea, lightning comes most in the night and early morning, as it does over the world's oceans. Part of that contrast is the instrument: the lightning mappers catch roughly 11 to 16% fewer flashes by day than by night.

The busiest days of the year

The ten days with the most flashes in the frame, and what the National Weather Service in San Juan said was happening.

The year’s longest flash

On October 16, 2025 at 9:25 PM AST, as the stalled front's storms built toward the year's busiest night, GOES-19 recorded one flash of 85 pulses of light over 1.74 seconds, east of St. Croix. Its pulses spread over 102 km (63 miles).

GOES-19 counts pulses as one flash while each falls within 16.5 km and 330 milliseconds of the flash, and that rule sometimes joins pulses that cannot belong together: of the 4,000 most spread-out flashes in the region this year, 1,030 carried a pulse far from the rest within the same split second. So each flash is measured over the pulses that chain together within 20 km, and a flash only counts if its duration can explain its length. By that measure this was the longest over the islands; the longest in the wider region was 112 km, on June 12, 2026.

The world record, certified by the World Meteorological Organization in July 2025, is 829 km, from eastern Texas to near Kansas City in October 2017.

Lightning yesterday

GOES-19 recorded 158 flashes in the frame on October 7, 2026.

Lightning safety on the water and at the beach

How GOES-19 sees lightning

GOES-19 has watched the Americas from 75.2° W since April 7, 2025, when it became NOAA's GOES-East. Its Geostationary Lightning Mapper is a camera that takes 500 pictures a second at 777.4 nanometres, the light oxygen gives off in a lightning channel, with pixels about 8 km across (14 km at the edge of its view). A pixel that lights up is an event; the events touching each other in one frame are a group, one pulse of light; groups within 16.5 km and 330 milliseconds are one flash.

It sees all lightning, in the cloud and to the ground, and cannot tell the two apart. Most lightning never reaches the ground, so this map shows flashes, not strikes, each placed to within about 3 to 4 km.

It does not see every flash. NOAA's validation of GOES-19 from April 2025 to February 2026 found it detects about 82% of the flashes ground networks report, and about 92% by a statistical estimate, with fewer by day than by night and fewer of the smallest flashes. Its lightning data reached NOAA's Provisional maturity on March 13, 2025 and Full maturity on March 18, 2026.

After a safe hold on July 15, 2026, GOES-19 sent no lightning data for 47 hours. NOAA has since reported extra false flashes in the tropics, mostly between 11 AM and 3 PM AST; the islands' record shows no sign of them (see the method).

How this map is made

Every 20-second GOES-19 GLM L2 LCFA file in NOAA's open bucket for the past year, October 8, 2025 to October 7, 2026 (days and hours in Atlantic Standard Time): 1,567,858 files, 99.4% of the year. The gaps: 47 hours from 4:22 PM AST on July 15 to 3:27 PM on July 17, 2026, the satellite's safe hold; about 3 hours on September 22, 2026; and a few minutes on other days.

Flashes with a good quality flag only; 3.9% of the region's flashes carried a degraded flag and are left out. Each flash is placed at its energy-weighted centre. The frame is 17.3–19.2° N and 63.85–65.95° W, Culebra and Vieques to Anegada and St. Croix; the region, for the hour-by-hour map and the year's longest flash, is 15.9–20.9° N and 61.2–69.4° W, from the east of the Dominican Republic to Guadeloupe.

By island: a flash whose centre fell over the island or within 10 km of its shoreline (TIGER 2023 for the U.S. Virgin Islands, OpenStreetMap for the BVI). Land and sea by hour: every second flash in the region, classed by the coastlines of Puerto Rico, the Virgin Islands, the east of the Dominican Republic and the Leeward Islands in it.

The year's longest flash: GOES-19's flash product sometimes attaches a pulse hundreds of km from the rest in the same milliseconds, so each flash's length is measured over its pulses that chain together within 20 km (the farthest two of them), and a flash is kept only if that length is no more than 30 km plus 200 km for every second it lasted. 1,030 of the 4,000 most spread-out flashes in the region carried such a stray pulse; 17 more were too long for their duration.

False flashes after the safe hold: NOAA reported extra false flashes in the tropics from July 17, 2026, mostly between 15:00 and 19:00 UTC. False flashes are mostly isolated, so we counted the flashes with no other flash within 25 km and 20 minutes: their share rose only from 0.5% before the safe hold to 0.6% after, and no spot lit up again and again. At most about 500 of the 430,000 flashes in the wider box since July 17, about 0.1%, could be false; we left them in.

The globe: every good flash GOES-19 recorded between 8° and 52° N and 52° and 132° W in the past year, counted on a 0.1° grid.

1. NOAA GOES-19 Geostationary Lightning Mapper, L2 LCFA files (NOAA Open Data Dissemination on AWS)
2. NOAA NESDIS: GOES-19 now operational as GOES East (April 7, 2025)
3. NOAA NESDIS: Geostationary Lightning Mapper
4. GOES-19 GLM L2 Full Validation, Product Performance Guide (NOAA OSPO, 2026)
5. NOAA OSPO notice: GOES-19 GLM Products Degraded (August 24, 2026)
6. NWS San Juan Area Forecast Discussions (Iowa Environmental Mesonet archive)
7. National Weather Service lightning safety
8. NWS: lightning safety outdoors (beaches, boats, divers)
9. NOAA U.S. Coast Pilot 5, chapter 14: Puerto Rico and the Virgin Islands (meteorological table)
10. Rudlosky et al. (2019), Initial Geostationary Lightning Mapper observations, GRL 46
11. Virts and Koshak (2025), Bayesian analysis of the detection performance of the GLMs, JTECH 42
12. Albrecht et al. (2016), Where are the lightning hotspots on Earth? BAMS 97
13. Holle (2018), U.S. lightning deaths by state, 1959–2017 (NWS)
14. NOAA NCEI Storm Events Database, 2025
15. National Hurricane Center: Dolly, discussion 5 (August 28, 2026)
16. WMO certifies megaflash lightning record in USA (July 31, 2025)