Hurricanes and Tornadoes That Hit Grasonville, MD

The nearest NOAA station with 1991–2020 climate normals is Royal Oak 2 SSW, MD, 17 miles south of Grasonville at 10 feet. July is the warmest, with an average high of 88°F and low of 70°F; January is the coolest, at 45°F and 29°F. August is the wettest at 4.8 inches of precipitation on average and February the driest at 3.1 inches; the year adds up to 47.7 inches over 79 days with at least a tenth of an inch. June to November, the hurricane season months, bring 53% of the year's precipitation (25.1 of 47.7 inches); the other six months are drier. September has brought the most of the 46 tropical systems that passed within 75 miles (17); a normal September there has highs of 80°F and 4.2 inches of precipitation. Highs reach 90°F on about 32 days a year, almost all from May to September. Lows fall below freezing on about 69 nights a year. Snowfall averages 14.1 inches a year, most of it in January. That 47.7 inches is more than at 31 of the 41 Maryland stations used on this site (76%). Centreville, 11 miles northeast, has its own station (Chestertown, MD): 46.1 inches a year, 1.6 less than here, and a July average high of 87°F against 88°F.

Water temperature at the NOAA tide station Annapolis, MD, 15 miles west, averaged 85°F in July and 42°F in January over 2021–2025. It averaged 80°F or warmer from July to August. Sea level at the Annapolis tide gauge, 15 miles from Grasonville, has risen 1.52 ± 0.04 inches per decade from 1928 to 2025, NOAA's linear trend; at that pace it is 15.2 inches in a hundred years. That is faster than at 92 of the 144 U.S. gauges with a NOAA trend.

Since 1996, the National Weather Service has logged 173 flood, rain, thunderstorm wind and lightning events that began within 10 miles of Grasonville: 112 thunderstorm wind reports, 30 heavy rain events, 21 flash floods, 6 floods and 4 lightning strikes. They killed 0 people and injured 1, and the NWS estimated $2.0 million in property and crop damage. The strongest thunderstorm gust on record here was 102 mph, on June 2, 2000. August has had the most flash floods, 13 of 21. Of the 239 Maryland cities on this site with a flash flood on record, 73 have had fewer than Grasonville.

Flood insurance policyholders in Grasonville's ZIP code 21638 have filed 314 claims with the National Flood Insurance Program since 1979, and were paid $5.6 million for buildings and contents, in the dollars of each year. The most came from Hurricane Isabel in 2003: 251 claims (80% of all) and $4.6 million. 87% 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, 137 have fewer than Grasonville.