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What is the Risk of a Large
Snowfall in the Washington Area during a Typical Winter?
Below is a table of numbers that represent the calculated risk for a single
snow event. It does not look at cumulative or multiple events. To calculate the
risk for "12 or more inches", all events of more than 12 inches
including those with 18 or 24 inches were used. During the 100 year period from
1897 through 1997, snowfall events of 12 or more inches occurred 15 times.
National Airport and Downtown DC
* Based on 100 years of official data (1897-1997)
| Snowfall Amount |
Return Frequency |
| 24 or more inches |
1 in 100 years |
| 18 or more inches |
1 in 50 years |
| 16 or more inches |
1 in 20 years |
| 14 or more inches |
1 in 12 years |
| 12 or more inches |
1 in 7 years |
| 10 or more inches |
1 in 3 years |
| 8 or more inches |
1 in 2 year |
| 4 or more inches |
2 per year |
| 1 or more inches |
5 per year |
The Greater Washington Metropolitan Area
(Northern Montgomery, Western Fairfax, Western Prince
William and Loudoun)
* Based on 150% of
the official snowfall amount recorded over 100 years.
| Snowfall Amount |
Return Frequency |
| 24 or more inches |
1 in 25 years |
| 18 or more inches |
1 in 7 years |
| 14 or more inches |
1 in 3 years |
| 10 or more inches |
1 in 2 years |
| 8 or more inches |
1 per year |
| 4 or more inches |
3 times per year |
| 1 or more inches |
6 times per year |
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Numbers Produced by Barbara McNaught Watson
Warning Coordination Meteorologist
NWS Baltimore-Washington Forecast Office
| 
www.nws.noaa.gov 
