The climate here is characterized by cold, snowy winters and mild summers, which vary greatly from north to south and at higher elevations. The jet stream is located near the state, and gives it highly variable weather patterns.
Our State’s Climate
The extreme northern and western portions of the state are the least influenced by the moderating effects of the Gulf of Maine and thus experience more extreme cold temperatures. The southeast, with its lower elevations and proximity to the Atlantic Ocean, is somewhat warmer. There are four main climate hazards in our region of concern, including: 1) rising average temperatures, 2) rising precipitation, 3) extreme weather events/storms, and 4) sea level rise.
Temperatures in New Hampshire have risen more than 3°F since 1900. The greatest warming has occurred in the winter, with an increase of more than 4°F over the same period. Spring frosts are ending earlier and the fall frosts starting later, extending the warm season.
Total annual precipitation for New Hampshire has been above average over the latest 16 year period (2005–2020). A state-level analysis for southern New Hampshire found that the rate of increase in annual precipitation from 1970 to 2012 was at least double the long-term (1895–2012) average because of the high values occurring early in this century.
More Extreme Weather Events
Extreme weather events common to New Hampshire include severe coastal storms, winter storms, cold waves, thunderstorms, floods, and tropical cyclones. Winter storms and snow are an important feature of New Hampshire’s climate. The Federal Emergency Management Agency made 15 major disaster declarations for New Hampshire over the last 10 years (2011–2020); almost half (7) were related to severe storms and flooding.
Rising Sea Levels
Since 1900, global average sea level has risen by about 7–8 inches. Coastal communities in Portsmouth are particularly vulnerable to sea level rise and coastal storm surge. From 1926 to 2019, tidal-gauge records showed that sea level in Portsmouth Harbor had risen more than half a foot (8.04 inches), nearly the same as the global average.