Hurricanes and Tornadoes That Hit Dennis, MA

The nearest NOAA station with 1991–2020 climate normals is Hyannis Barnstable Municipal Airport, MA, 7 miles southwest of Dennis at 55 feet. July is the warmest, with an average high of 81°F and low of 65°F; January is the coolest, at 40°F and 24°F. December is the wettest at 4.7 inches of precipitation on average and July the driest at 2.7 inches; the year adds up to 44.8 inches over 77 days with at least a tenth of an inch. June to November, the hurricane season months, bring 48% of the year's precipitation (21.4 of 44.8 inches); the other six months are wetter. September has brought the most of the 64 tropical systems that passed within 75 miles (20); a normal September there has highs of 73°F and 3.9 inches of precipitation. Highs reach 90°F on about 2 days a year, almost all from July. Lows fall below freezing on about 109 nights a year. That 44.8 inches is more than at 11 of the 65 Massachusetts stations used on this site (17%). Brewster, 6 miles east, has its own station (Chatham Municipal Airport, MA): 45.2 inches a year, 0.4 more than here, and a July average high of 79°F against 81°F.

Water temperature at the NOAA tide station Chatham, MA, 13 miles east, averaged 69°F in August and 39°F in February over 2021–2025. No month averaged 80°F. Sea level at the Woods Hole tide gauge, 29 miles from Dennis, has risen 1.24 ± 0.03 inches per decade from 1932 to 2025, NOAA's linear trend; at that pace it is 12.4 inches in a hundred years. That is faster than at 73 of the 144 U.S. gauges with a NOAA trend.

Since 1996, the National Weather Service has logged 54 flood, rain, thunderstorm wind and lightning events that began within 10 miles of Dennis: 24 thunderstorm wind reports, 20 floods, 5 flash floods, 4 lightning strikes and 1 heavy rain event. None is recorded as killing or injuring anyone; the NWS estimated $2.9 million in property and crop damage. The strongest thunderstorm gust on record here was 90 mph, on July 23, 2019. August has had the most flash floods, 3 of 5. Of the 339 Massachusetts cities on this site with a flash flood on record, 40 have had fewer than Dennis.

Flood insurance policyholders in Dennis's ZIP code 02638 have filed 28 claims with the National Flood Insurance Program since 1978, and were paid $206,000 for buildings and contents, in the dollars of each year. 50% of the claims carry the name of a storm or flood event; the rest have no event name. Of the 229 Massachusetts cities on this site with 10 or more claims, 87 have fewer than Dennis.