Hurricanes and Tornadoes That Hit Potomac, MD

The nearest NOAA station with 1991–2020 climate normals is Rockville 1 NE, MD, 5 miles northeast of Potomac at 440 feet. July is the warmest, with an average high of 87°F and low of 69°F; January is the coolest, at 42°F and 27°F. June to November, the hurricane season months, bring 53% of the year's precipitation (21.9 of 41.5 inches); the other six months are drier. October has brought the most of the 27 tropical systems that passed within 75 miles (9); a normal October there has highs of 66°F and 3.5 inches of precipitation. Highs reach 90°F on about 23 days a year, almost all from May to August. Lows fall below freezing on about 86 nights a year. That 41.5 inches is more than at 5 of the 41 Maryland stations used on this site (12%). Bethesda, 5 miles southeast, has its own station (Dalecarlia Rsvr, MD): 48.3 inches a year, 6.8 more than here, and a July average high of 88°F against 87°F.

Water temperature at the NOAA tide station Washington, DC, 15 miles southeast, averaged 84°F in July and 39°F in January over 2021–2025. It averaged 80°F or warmer from July to August. Sea level at the Washington tide gauge, 15 miles from Potomac, has risen 1.40 ± 0.05 inches per decade from 1924 to 2025, NOAA's linear trend; at that pace it is 14.0 inches in a hundred years. That is faster than at 84 of the 144 U.S. gauges with a NOAA trend.

Since 1996, the National Weather Service has logged 1,242 flood, rain, thunderstorm wind and lightning events that began within 10 miles of Potomac: 767 thunderstorm wind reports, 243 floods, 222 flash floods, 9 lightning strikes and 1 heavy rain event. They killed 10 people and injured 24, and the NWS estimated $31.7 million in property and crop damage. The strongest thunderstorm gust on record here was 90 mph, on July 25, 2010. July has had the most flash floods, 107 of 222. Of the 239 Maryland cities on this site with a flash flood on record, 224 have had fewer than Potomac.

Flood insurance policyholders in Potomac's ZIP code 20854 have filed 53 claims with the National Flood Insurance Program since 1978, and were paid $550,000 for buildings and contents, in the dollars of each year. The year with the most claims was 2019, with 11. 4% of the claims carry the name of a storm or flood event; the rest have no event name. Of the 150 Maryland cities on this site with 10 or more claims, 84 have fewer than Potomac.