Norton climate

Norton Frost Dates and Growing Season

NOAA 1991-2020 normals for Norton Dam, 4.8 km from Norton, elevation 2346 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Norton Dam. 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 1 and the first fall freeze around October 12, a growing season of about 162 days.

Median at 36°F
last May 10, first October 3
Median at 32°F
last May 1, first October 12
Median at 28°F
last April 21, first October 21

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°FMay 26May 19May 15May 12May 10May 7May 5May 2Apr 28
32°FMay 15May 9May 5May 3May 1Apr 29Apr 26Apr 22Apr 17
28°FMay 3Apr 30Apr 27Apr 24Apr 21Apr 17Apr 14Apr 10Apr 6
24°FApr 25Apr 19Apr 15Apr 12Apr 9Apr 6Apr 3Mar 31Mar 24
20°FApr 14Apr 10Apr 6Apr 3Mar 31Mar 28Mar 24Mar 20Mar 13
16°FApr 7Apr 2Mar 29Mar 24Mar 21Mar 16Mar 13Mar 8Mar 3

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 19Sep 25Sep 29Oct 1Oct 3Oct 5Oct 8Oct 11Oct 15
32°FSep 29Oct 3Oct 6Oct 10Oct 12Oct 14Oct 17Oct 20Oct 22
28°FOct 6Oct 12Oct 16Oct 19Oct 21Oct 23Oct 25Oct 28Nov 1
24°FOct 16Oct 20Oct 23Oct 26Oct 29Oct 31Nov 3Nov 6Nov 11
20°FOct 22Oct 27Oct 31Nov 3Nov 5Nov 9Nov 12Nov 16Nov 21
16°FOct 30Nov 3Nov 7Nov 11Nov 15Nov 18Nov 22Nov 26Dec 1

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°F162156152148144141137133125
32°F180174170166162158154150144
28°F201194189185181177173168161
24°F223215210206202198194188182
20°F244235230225220216211205197
16°F263255249244239234229222214

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
6,015
Cooling degree days, base 65°F
1,171
Growing degree days, base 40°F
5,698
Growing degree days, base 45°F
4,527
Growing degree days, base 50°F
3,494
Growing degree days, base 55°F
2,590
Growing degree days, base 60°F
1,818

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18100
February97703
March769031
April4605117
May19459348
June24241668
July2400863
August6323783
September90130495
October40711164
November782021
December1,12500

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 4.8 km from Norton. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00145852 (Norton Dam). Public domain.