Data sources & licences
This site is built entirely on open data and open-source software. Thank you to everyone who collected, shared and maintains it. Here is exactly what we use and the licence each part comes with.
- Data version
- NOAA Storm Prediction Center actual tornadoes, 1950 to 2025 (file 1950-2025_actual_tornadoes.csv, downloaded 2026-10-12): 73,458 tornadoes. Census cartographic boundaries 2020.
- Last refreshed
- 2026-10-13
NOAA Storm Prediction Center
Credit: Tornado records from the NOAA Storm Prediction Center, Severe Weather Database (spc.noaa.gov), US government, public domain
Used for: Every tornado on the map: its date, rating, path, length, width, injuries and deaths.
Licence: Public domain (US government work)
Source: https://www.spc.noaa.gov/wcm/
US Census Bureau
Credit: State and county boundaries, place and ZIP code (ZCTA) gazetteers from the US Census Bureau, public domain
Used for: State and county boundaries (2020 cartographic boundary files, used to count tornadoes in each place) and town and ZIP code positions for search.
Licence: Public domain (US government work)
Source: https://www.census.gov/geographies/mapping-files/time-series/geo/cartographic-boundary.html
GeoNames
Credit: GeoNames (geonames.org), CC BY 4.0
Used for: Town populations, used to name notable tornadoes after the nearest sizeable town and to order search results.
Licence: CC BY 4.0
Source: https://www.geonames.org/
OpenStreetMap
Credit: © OpenStreetMap contributors, basemap by Protomaps, ODbL
Used for: The basemap.
Licence: ODbL
Source: https://protomaps.com/
Software
The map is drawn with MapLibre GL JS and PMTiles, and the site is built with Astro. These are open-source projects under their own licences.
Using our images and embeds
Images you download from the map and the embed code both carry the credits above. Please leave them in place.
The tornado record in numbers
The map is built from the Storm Prediction Center "actual tornadoes" file 1950-2025_actual_tornadoes.csv, downloaded on 2026-10-12. It has 73,458 rows, one for each tornado from 1950 to 2025. The file's SHA-256 checksum is 2b2679ead1920ab9…. When the Storm Prediction Center publishes a newer year, the site will be rebuilt from the new file and this page will show the new range.
36,577 of the tornadoes have no recorded end point and are drawn as dots at the start. 1,546 have no rating (all from 2007 onwards). 670 crossed a state line.
How the records are counted
- The SPC actual-tornadoes file has one row per tornado (every row sg=1, the whole track). Multi-state tornadoes are one row. National count is the row count.
- A tornado belongs to every county its track touches (start-to-end line buffered by half its width), plus counties listed by SPC. State counts include every state touched, so they can sum to more than the national count.
- F/EF4 or 5, or 3 or more fatalities, or F/EF3 with at least 1 fatality.
- Tornadoes with no end point are drawn as points at the start.
- F scale before 1 February 2007, EF scale from that date. Rating -9 is unknown.
A place page counts every tornado whose path touches it. The state and county pages list a county only if tornadoes have touched it, and a county gets a page that search engines can index once it has at least 3 tornadoes.
Ratings
Tornadoes are rated on the Fujita (F) scale before 1 February 2007 and on the Enhanced Fujita (EF) scale from that date, the day the National Weather Service switched. The map and the pages label each tornado with the scale in use at the time. The two scales are close but not identical, so be careful when comparing across the change.
What is missing
The record starts in 1950. The Tri-State tornado of 18 March 1925, among others, is therefore not on the map.