Severe Weather Climatology

Tornado Events by County
from 1950 through 2022

Most Recent and Strongest Tornadoes By County

By Year (T3)

PA Tornado Magnitude and Frequency by Month
 

PA Tornadoes by Time of Day (Hour)

By Magnitude (T6)

Severe Weather Database

See All Tornado Events for a specific County:

Search for Past Tornado, Severe Wind Gust and Hail Events
(from NOAA NCEI Storm Data, 1/1/1950 through roughly 3 months ago)

The EF Scale, which became operational on February 1, 2007, is used to assign a tornado a 'rating' based on estimated wind speeds and related damage. When tornado-related damage is surveyed, it is compared to a list of Damage Indicators (DIs) and Degrees of Damage (DoD) which help estimate better the range of wind speeds the tornado likely produced. From that, a rating (from EF0 to EF5) is assigned.

The EF Scale was revised from the original Fujita Scale to reflect better examinations of tornado damage surveys so as to align wind speeds more closely with associated storm damage. The new scale has to do with how most structures are designed.

*** IMPORTANT NOTE ABOUT EF SCALE WINDS: The EF scale still is a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to the 28 indicators listed below. These estimates vary with height and exposure. Important: The 3 second gust is not the same wind as in standard surface observations. Standard measurements are taken by weather stations in open exposures, using a directly measured, "one minute mile" speed.

The NWS is the only federal agency with authority to provide 'official' tornado EF Scale ratings. The goal is assign an EF Scale category based on the highest wind speed that occurred within the damage path. First, trained NWS personnel will identify the appropriate damage indicator (DI) [see list below] from more than one of the 28 used in rating the damage. The construction or description of a building should match the DI being considered, and the observed damage should match one of the 8 degrees of damage (DOD) used by the scale. The tornado evaluator will then make a judgment within the range of upper and lower bound wind speeds, as to whether the wind speed to cause the damage is higher or lower than the expected value for the particular DOD. This is done for several structures not just one, before a final EF rating is determined.

Other background information:

• EF Scale website at the Storm Prediction Center (SPC)
• 95-page PDF covering the development of the EF Scale

Severe Thunderstorm Events by County
(Hail and Wind Damage Combined)
from 1950 to 2018.

W3

W4

W5

W6

W7

H1

H2

H3

H4

H5

H6

H7

Flooding Events by County
(River Flooding and Flash Floods Combined)
from 1950 to 2004.

   

F2

F3

F4

F5

F6

F7