Methodology: how the storm counts are computed

Every number on this site is computed from one public dataset by one repeatable process, described here in full.

The source: NOAA HURDAT2

All storm data comes from HURDAT2, the Atlantic and Northeast Pacific hurricane databases published by NOAA's National Hurricane Center at nhc.noaa.gov/data. It is the post-season best-track record: for each storm, a position, maximum sustained wind in knots, pressure and a status code, normally every six hours.

This build uses hurdat2-1851-2025-02272026.txt (Atlantic: 2,004 storms, 55,605 track points, 1851–2025) and hurdat2-nepac-1949-2025-02272026.txt (Northeast Pacific: 1,262 storms, 32,026 points). File names are read from the NOAA index at build time, never hard-coded, so revisions are picked up automatically. County coordinates come from the Census Bureau's 2024 Gazetteer: 3,222 counties and equivalents.

What counts as a storm

A storm counts for a county when the closest point on its interpolated track came within 50 miles of that county's Census internal point. Bands of 25 and 100 miles are reported too, because 50 is a choice, not a natural boundary: 25 miles is near a direct hit, 100 the rough reach of a large hurricane's outer wind and rain. Across all 3,222 counties the same database gives 20,611 passes within 25 miles, 42,729 within 50 and 91,591 within 100.

So when a page says 34 storms, it means 34 separate tropical or subtropical cyclones in HURDAT2 whose track came within 50 miles of that county's centre. It does not mean 34 hurricanes, 34 landfalls there, or 34 damaging storms; damage, deaths and rainfall are not in HURDAT2 and are not modelled here. Counties with fewer than 10 qualifying storms are not published: 1,019 county pages exist, not one per county.

Why six-hourly fixes are interpolated to one hour

Storms move a long way in six hours. Across the 53,601 consecutive fix pairs in the Atlantic file, the mean distance from one fix to the next is 80.9 miles, the median 71.0 miles, and one leg in ten exceeds 143 miles. Measured only at the recorded fixes, a storm that passed a county between two of them is reported as distant.

Each track is therefore interpolated linearly in latitude, longitude and wind to one-hour steps before any distance is measured; the 87,631 recorded fixes become 502,435 hourly points. Hurricane Charley's fixes on 14 August 2004 put it at 28.1N 81.6W at 0000Z and 30.1N 80.8W at 0600Z, a 146-mile leg. Distances from the centre of Volusia County, Florida:

On the six-hourly fixes alone Charley's closest approach is 71.3 miles and it drops out of Volusia County's record entirely. Interpolated, it is a 3.7-mile pass at hurricane strength, 75 knots. Nor is it one odd case: of the 42,729 county-storm pairs qualifying at 50 miles, 10,057 would measure farther on the raw fixes.

How distance is measured

Distances are great-circle distances (haversine) on a spherical Earth of radius 3,958.7613 miles. The county end of each measurement is the Census Gazetteer internal point (INTPTLAT/INTPTLONG), a published coordinate inside the county, near its geographic centre.

It is a simplification that cuts one way: distance is measured to the county's centre, not to its nearest boundary. A storm listed as passing 55 miles from a large county may in fact have crossed its coastline. Large counties are therefore treated conservatively — their counts are if anything too low.

Status and category at closest approach

Every value on a storm's row is read at its closest approach to that county, not its peak elsewhere: a Category 5 that had weakened on the way is listed as whatever it then was.

Status uses the HURDAT2 codes: HU hurricane, TS tropical storm, TD tropical depression, SS and SD subtropical storm and depression, EX extratropical, LO remnant low, DB disturbance. Status is not interpolated — it is carried forward from the last six-hourly observation at or before closest approach. Wind is, and Saffir–Simpson category comes from that interpolated wind: Category 1 at 64 knots, 2 at 83, 3 at 96, 4 at 113, 5 at 137. Extratropical systems and remnant lows get no category.

Why extratropical passes sit outside the headline count

Headline counts include only tropical and subtropical systems (HU, TS, TD, SS, SD); passes by systems already extratropical, a remnant low or a disturbance are counted separately and stated under each storm table. They are not a rounding error. Of the 54,776 passes within 50 miles of a county centre, 12,047 — 22% — were non-tropical: 10,411 extratropical, 1,624 remnant lows, 12 disturbances. Counting them would inflate every county's total by about a fifth; dropping them silently would hide a fifth of the record.

Known limitations

• Older records are weaker. 371 of the 2,004 Atlantic storms predate 1900, their positions drawn from ship logs, newspaper accounts and landfall damage.
• Storms at sea were under-recorded. Before aircraft reconnaissance in the 1940s and satellites in the 1960s, a storm that missed shipping lanes and land could go unrecorded; early counts lean toward those that reached populated coasts.
• HURDAT2 changes. NHC revises the database each year, usually in late winter, and its reanalysis keeps rewriting older seasons, so counts here can change between builds.
• The record ends with 2025. The 2026 season is not included.
• Averages are not forecasts. An interval such as "one every 4.1 years" is the record span divided by the number of storms: it describes the past and predicts nothing. For anything forward-looking, see nhc.noaa.gov.

How often this rebuilds

The site is regenerated from the source files, never edited by hand. The pipeline re-checks the NOAA index for new HURDAT2 revisions and rebuilds every year on 5 March, after NHC publishes the revised database for the previous season. Each page footer names the source files and the date they were accessed, so any figure traces back to a specific version. If a number here looks wrong, check it against HURDAT2; corrections are welcome at contact@stormpast.com.