Waterville Valley climate

Waterville Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Waterville Valley Nepp, 1.1 km from Waterville Valley, elevation 1429 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Waterville Valley Nepp. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 15 and the first fall freeze around September 28, a growing season of about 134 days.

Median at 36°F
last May 29, first September 16
Median at 32°F
last May 15, first September 28
Median at 28°F
last May 2, first October 9

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 11Jun 6Jun 3May 31May 29May 26May 23May 20May 16
32°FMay 29May 25May 21May 18May 15May 13May 10May 7May 3
28°FMay 14May 10May 7May 4May 2Apr 30Apr 29Apr 25Apr 22
24°FMay 1Apr 28Apr 24Apr 22Apr 19Apr 17Apr 13Apr 10Apr 6
20°FApr 19Apr 15Apr 12Apr 9Apr 6Apr 4Apr 2Apr 1Mar 28
16°FApr 7Apr 5Apr 3Apr 1Mar 31Mar 29Mar 26Mar 21Mar 17

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 4Sep 8Sep 11Sep 14Sep 16Sep 19Sep 22Sep 25Sep 30
32°FSep 13Sep 18Sep 22Sep 25Sep 28Oct 1Oct 3Oct 5Oct 11
28°FSep 26Oct 1Oct 3Oct 6Oct 9Oct 13Oct 17Oct 21Oct 29
24°FOct 9Oct 15Oct 19Oct 23Oct 26Oct 30Nov 1Nov 4Nov 10
20°FOct 24Nov 1Nov 3Nov 5Nov 8Nov 12Nov 14Nov 18Nov 23
16°FNov 8Nov 12Nov 14Nov 18Nov 20Nov 23Nov 26Nov 30Dec 5

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F1271211171131101071039790
32°F150145140137134129126122115
28°F177170166162158155151146141
24°F209202198193189184179174167
20°F233227222218214211207202195
16°F252246242238235231227222217

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
8,558
Cooling degree days, base 65°F
160
Growing degree days, base 40°F
3,343
Growing degree days, base 45°F
2,420
Growing degree days, base 50°F
1,634
Growing degree days, base 55°F
980
Growing degree days, base 60°F
476

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,49700
February1,31300
March1,19300
April767013
May4285107
June15925321
July4868485
August7946432
September25515235
October619137
November92404
December1,27600

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 1.1 km from Waterville Valley. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00278961 (Waterville Valley Nepp). Public domain.