Frost Dates in New Hampshire

At the middle station of the 46 in New Hampshire where a freeze comes every year, the last spring frost (50%) is May 7 and the first fall frost October 5, a freeze-free season of 148 days. The last frost is earliest at Manchester (Manchester Airport, NH, April 21) and latest at Colebrook (Colebrook 3SW, NH, May 31), 40 days apart. The season runs from 112 days at Colebrook to 180 at Manchester.

29 of these stations were also in NOAA's previous normals, for 1981–2010. Between the two, the median station's freeze-free season grew 8 days longer, with the last spring frost 4 days earlier and the first fall frost 3 days later; the season lengthened at 25 stations and shortened at 4. The two periods share twenty years, so the change reflects mostly 2011–2020 against 1981–1990.