The counties with the most storm days per square mile
Days with a storm record per 1,000 square miles since 1996, counties of 100 square miles or more
Per 1,000 square miles from 1996 through June 30, 2026, Philadelphia County, PA has the most days with a storm record per square mile: 941 days on 134 square miles of land, 7,005 per 1,000 square miles, followed by Carson City (city), NV and Delaware County, PA.
Source: NOAA NCEI Storm Events Database, 1996 to June 30, 2026; land area: Census Bureau 2024 Gazetteer.
How this ranking is measured
The days from 1996 (the first year all event types were recorded) to the newest record on which NOAA filed at least one storm record for the county, divided by its land area. Days, not records: the National Weather Service files a zone-wide storm once per forecast zone, so a county covered by several zones collects several records for one storm but one day. A day with a zone record counts on every county the zone covers. Counties under 100 square miles (independent cities) are left out: a few records on a small area would top the list.
Which states hold the top 100?
23 states have a county in the top 100; New Jersey has the most (15). Smaller counties rank high on this measure: a day with a forecast-zone record counts in full on every county the zone covers, however small. Neighbouring counties often rank together (four of the top ten lie around Philadelphia), which points at how the local records are filed as much as at the weather, so read a county's rate beside its own record and its neighbours'.
New Jersey15
Kentucky13
Virginia10
Maryland10
Illinois9
Pennsylvania6
West Virginia5
Indiana4
Wisconsin4
New York3
Colorado3
North Carolina3
Nevada2
Hawaii2
Rhode Island2
Georgia2
Tennessee1
New Mexico1
Delaware1
Massachusetts1
Texas1
Minnesota1
Florida1
Source: NOAA NCEI Storm Events Database, 1996 to June 30, 2026.