New Hampshire - State Climate Summaries 2022

Extreme weather events common to New Hampshire include severe coastal storms, winter storms, cold waves, thunderstorms, floods, and tropical cyclones. 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. The state’s coastline is highly vulnerable to damage from winter coastal storms (known as nor’easters) and tropical cyclone events (hurricanes and tropical storms). These cyclonic storms often result in wide-scale flooding, property damage, and coastal erosion. Superstorm Sandy, in 2012, was the most extreme and destructive event to affect the northeastern United States in 45 years and the fourth costliest in the Nation’s history. The most destructive element of Sandy was storm surge, with heights reaching 3.2 feet above normal tide levels in New Hampshire. The state suffered more than $75 million in economic losses.

Winter storms are an important feature of New Hampshire’s climate. In most years, several storms depositing 5 or more inches of snow will affect the state. Seasonal snowfall totals for 2014–15 were well above the long-term average of about 60 inches across southern portions of the state; for example, Concord received more than 90 inches. Concord also received more than 85 inches during 2016–17 and 2017–18. However, the 2007–08 season holds the record for the highest seasonal snowfall in Concord (118 inches). Although these recent winters were snowy, overall snowfall has been declining at a majority of stations. During the 2015–16 season, Concord received about half of its normal snowfall. The number of snow-covered days is also decreasing throughout the state.

Under a higher emissions pathway, historically unprecedented warming is projected during this century (Figure 1). Even under a lower emissions pathway, annual average temperatures are projected to most likely exceed historical record levels by the middle of this century. However, a large range of temperature increases is projected under both pathways, and under the lower pathway, a few projections are only slightly warmer than historical records. Heat waves are projected to increase in intensity, while cold waves are projected to become less intense. In response to cold season warming, the state can expect more precipitation falling as rain rather than snow, earlier lake ice-out dates, and a decline in days with snow cover. This has implications for winter tourism. By midcentury (under a higher emissions pathway), the annual number of days above 90°F is projected to increase by up to 30 days in southern New Hampshire and up to 10 days in the north.

Annual average precipitation is projected to continue to increase for New Hampshire over this century, particularly during the winter (Figure 5). This trend is characteristic of a large area of the Northern Hemisphere in the higher mid-latitudes that is projected to see increases in precipitation totals. The frequency of extreme precipitation events is also expected to more than double in the region by the end of this century under a higher emissions pathway. These precipitation projections may also result in increased flooding risks. The intensity of naturally occurring droughts is also projected to increase because of an increased rate of soil moisture depletion from higher temperatures during dry spells.