There is no overall trend in the number of hot days however, the number of warm nights has been above average since 2000. Long-term stations dating back to 1900 were not available for New Hampshire. Values for the contiguous United States (CONUS) from 1900 to 2020 are included for Figures 2a and 2b to provide a longer and larger context. The horizontal black lines show the long-term (entire period) averages for New Hampshire: (a) 8.1 days, (b) 1.2 nights, (c) 44.3 inches, (d) 12.1 inches. Bars show averages over 5-year periods (last bar is a 6-year average). Observed (a) annual number of hot days (maximum temperature of 90☏ or higher), (b) annual number of warm nights (minimum temperature of 70☏ or higher), (c) total annual precipitation, and (d) total summer (June–August) precipitation for New Hampshire from (a, b) 1950 to 1920 and (c, d) 1895 to 2020. Warmer winters are also reflected in a trend toward earlier ice-out dates on lakes and fewer nights below freezing.įigure 2. The 2010–2014 period had the lowest multiyear average of about 18 nights per year. This is reflected in the number of very cold nights, which has been below average since the early 1990s (Figure 3). The greatest warming has occurred in the winter, with an increase of more than 4☏ since 1900. Since 2000, the number of warm nights has been above average, with the 2000–2004 period having the highest multiyear average of about 2 nights per year (Figure 2b). The number of hot days has varied across the period of record (1950–2020 Figure 2a) however, the most recent period (2015–2020) had the highest multiyear average of about 9 days. Temperatures in New Hampshire have risen more than 3☏ since the beginning of the 20th century (Figure 1). Less warming is expected under a lower emissions future (the coldest end-of-year projections being about 2✯ warmer than the historical average green shading) and more warming under a higher emissions future (the hottest end-of-year projections being about 12✯ warmer than the hottest year in the historical record red shading). Historically unprecedented warming is projected during this century. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Shading indicates the range of annual temperatures from the set of models. Temperatures in New Hampshire (orange line) have risen more than 3☏ since the beginning of the 20th century. Projected changes for 2006–2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions). The statewide annual average (1991–2020 normals period) precipitation is 48.8 inches, with higher amounts occurring in the south and along the eastern border of the state and lower amounts in the west and north.įigure 1: Observed and projected changes (compared to the 1901–1960 average) in near-surface air temperature for New Hampshire. Average maximum temperatures in July range from 75☏ to 80☏ in the north and from 80☏ to 85☏ in the south. Coastal communities, such as the Portsmouth area, are even warmer, with average minimum temperatures ranging from 15☏ to 18☏. Average minimum temperatures in January are colder in the north (Lancaster: 2☏ to 7☏) and at higher elevations (Mount Washington: −5☏ to −1☏) than in the south (Concord: 12☏ to 15☏). The southeast, with its lower elevations and proximity to the Atlantic Ocean, is somewhat warmer. 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. Precipitation is frequent because several preferred storm tracks associated with the jet stream cross the state. The jet stream is often located near the state, particularly in the late fall, winter, and spring, and gives it highly variable weather patterns. Its climate is characterized by cold, snowy winters and mild summers. Its northerly latitude and geographic location expose the state to both the moderating and moistening influence of the Atlantic Ocean and the effects of hot and cold air masses from the interior of the continent. New Hampshire is located on the eastern margin of the North American continent.
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