Grand Canyon climate

Grand Canyon Frost Dates and Growing Season

NOAA 1991-2020 normals for Grand Canyon Np 2, 1 km from Grand Canyon, elevation 6785 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grand Canyon Np 2. 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 June 1 and the first fall freeze around October 3, a growing season of about 123 days.

Median at 36°F
last June 12, first September 24
Median at 32°F
last June 1, first October 3
Median at 28°F
last May 15, first October 12

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 29Jun 23Jun 19Jun 15Jun 12Jun 9Jun 7Jun 4May 31
32°FJun 17Jun 10Jun 5Jun 3Jun 1May 29May 25May 19May 12
28°FJun 2May 29May 23May 19May 15May 11May 6May 2Apr 28
24°FMay 18May 12May 6May 2Apr 29Apr 26Apr 23Apr 19Apr 14
20°FMay 3Apr 24Apr 18Apr 14Apr 10Apr 7Apr 3Mar 30Mar 19
16°FApr 7Apr 1Mar 27Mar 20Mar 16Mar 12Mar 9Mar 4Feb 27

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 10Sep 14Sep 18Sep 21Sep 24Sep 26Sep 29Oct 1Oct 5
32°FSep 22Sep 26Sep 29Oct 1Oct 3Oct 5Oct 7Oct 11Oct 15
28°FOct 1Oct 4Oct 7Oct 9Oct 12Oct 15Oct 18Oct 22Oct 28
24°FOct 9Oct 14Oct 17Oct 20Oct 24Oct 28Oct 31Nov 4Nov 8
20°FOct 19Oct 25Oct 29Nov 2Nov 5Nov 9Nov 13Nov 17Nov 21
16°FOct 29Nov 4Nov 9Nov 13Nov 17Nov 20Nov 23Nov 27Dec 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°F12011410910410097928780
32°F146139133128123119115110103
28°F172166159155149144140135126
24°F199192185181176172166160151
20°F234225218211206201195188178
16°F268259253247241236230222212

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
6,366
Cooling degree days, base 65°F
212
Growing degree days, base 40°F
3,967
Growing degree days, base 45°F
2,868
Growing degree days, base 50°F
1,957
Growing degree days, base 55°F
1,209
Growing degree days, base 60°F
623

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,03100
February87600
March79704
April605022
May3833141
June11035379
July21103547
August3261494
September16710297
October498068
November78205
December1,06600

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 km from Grand Canyon. 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 USC00023596 (Grand Canyon Np 2). Public domain.