Cascade climate

Cascade Frost Dates and Growing Season

NOAA 1991-2020 normals for Cascade 5 S, 5.8 km from Cascade, elevation 3360 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cascade 5 S. 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 21 and the first fall freeze around September 19, a growing season of about 120 days.

Median at 36°F
last June 8, first September 3
Median at 32°F
last May 21, first September 19
Median at 28°F
last May 7, first October 1

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 27Jun 20Jun 15Jun 13Jun 8Jun 4May 31May 27May 22
32°FJun 6Jun 1May 27May 23May 21May 17May 14May 10May 5
28°FMay 22May 17May 13May 9May 7May 3Apr 30Apr 27Apr 22
24°FMay 10May 4May 1Apr 28Apr 24Apr 21Apr 16Apr 12Apr 6
20°FApr 29Apr 24Apr 19Apr 14Apr 10Apr 7Apr 4Apr 1Mar 24
16°FApr 23Apr 13Apr 9Apr 5Apr 2Mar 30Mar 25Mar 18Mar 12

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°FAug 18Aug 25Aug 28Sep 1Sep 3Sep 7Sep 10Sep 15Sep 21
32°FSep 2Sep 8Sep 12Sep 16Sep 19Sep 22Sep 25Sep 29Oct 2
28°FSep 13Sep 20Sep 24Sep 28Oct 1Oct 2Oct 6Oct 10Oct 16
24°FSep 26Oct 1Oct 4Oct 8Oct 12Oct 15Oct 18Oct 22Oct 27
20°FOct 3Oct 9Oct 14Oct 18Oct 21Oct 25Oct 28Nov 1Nov 6
16°FOct 11Oct 18Oct 22Oct 26Oct 29Nov 1Nov 4Nov 9Nov 17

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°F11110297928882787163
32°F14213412912512011511010696
28°F166159153149145140137131124
24°F192184179173168163158152145
20°F216207202196191185179172165
16°F237227221215210205199192181

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
6,863
Cooling degree days, base 65°F
337
Growing degree days, base 40°F
4,202
Growing degree days, base 45°F
3,045
Growing degree days, base 50°F
2,088
Growing degree days, base 55°F
1,319
Growing degree days, base 60°F
737

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12204
February99504
March862017
April590043
May3584160
June14830335
July32147580
August48123542
September21229285
October538492
November845022
December1,11302

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 5.8 km from Cascade. 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 USC00241552 (Cascade 5 S). Public domain.