Magna climate

Magna Frost Dates and Growing Season

NOAA 1991-2020 normals for Garfield, 8.2 km from Magna, elevation 4298 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Garfield. 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 April 3 and the first fall freeze around November 4, a growing season of about 213 days.

Median at 36°F
last April 19, first October 23
Median at 32°F
last April 3, first November 4
Median at 28°F
last March 11, first November 13

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 5Apr 30Apr 26Apr 22Apr 19Apr 16Apr 12Apr 8Apr 2
32°FApr 19Apr 14Apr 11Apr 7Apr 3Mar 31Mar 27Mar 20Mar 11
28°FApr 6Mar 31Mar 26Mar 17Mar 11Mar 6Mar 2Feb 27Feb 20
24°FMar 12Mar 6Mar 2Feb 27Feb 23Feb 20Feb 16Feb 13Feb 7
20°FFeb 28Feb 23Feb 18Feb 15Feb 12Feb 7Feb 3Jan 30Jan 21
16°FFeb 19Feb 13Feb 8Feb 4Jan 31Jan 26Jan 17Jan 6Dec 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°FOct 9Oct 13Oct 17Oct 20Oct 23Oct 26Oct 29Nov 3Nov 7
32°FOct 18Oct 24Oct 28Nov 1Nov 4Nov 6Nov 9Nov 13Nov 17
28°FOct 27Nov 2Nov 6Nov 10Nov 13Nov 16Nov 20Nov 24Nov 28
24°FNov 5Nov 11Nov 15Nov 20Nov 23Nov 25Nov 29Dec 2Dec 9
20°FNov 13Nov 20Nov 25Nov 29Dec 2Dec 6Dec 11Dec 17Dec 25
16°FNov 23Nov 30Dec 6Dec 10Dec 15Dec 19Dec 26Jan 2Jan 11

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°F206199194189185180176172163
32°F238230224218213208203197190
28°F268261255249244238232225216
24°F293285279274269265259252243
20°F323313305300293288282275267
16°F354343334327321315308301290

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
95% 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
5,275
Cooling degree days, base 65°F
1,436
Growing degree days, base 40°F
6,152
Growing degree days, base 45°F
4,909
Growing degree days, base 50°F
3,826
Growing degree days, base 55°F
2,893
Growing degree days, base 60°F
2,103

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06500
February82701
March616036
April4127126
May16872378
June34243659
July1504968
August2439902
September52159558
October34812179
November716017
December1,03401

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 8.2 km from Magna. 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 USC00423097 (Garfield). Public domain.