Byron climate

Byron Frost Dates and Growing Season

NOAA 1991-2020 normals for Lovell, 9.3 km from Byron, elevation 3847 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lovell. 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 9 and the first fall freeze around September 29, a growing season of about 142 days.

Median at 36°F
last May 22, first September 19
Median at 32°F
last May 9, first September 29
Median at 28°F
last April 29, 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 6Jun 1May 27May 24May 22May 19May 15May 12May 7
32°FMay 25May 19May 15May 12May 9May 6May 3Apr 30Apr 27
28°FMay 12May 7May 3May 1Apr 29Apr 26Apr 23Apr 20Apr 15
24°FMay 2Apr 27Apr 23Apr 20Apr 17Apr 14Apr 10Apr 6Apr 2
20°FApr 21Apr 15Apr 11Apr 7Apr 4Apr 1Mar 30Mar 24Mar 17
16°FApr 11Apr 5Mar 31Mar 29Mar 24Mar 20Mar 15Mar 10Mar 6

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 7Sep 11Sep 14Sep 17Sep 19Sep 22Sep 24Sep 28Oct 2
32°FSep 16Sep 21Sep 24Sep 27Sep 29Oct 1Oct 4Oct 7Oct 11
28°FSep 25Sep 29Oct 2Oct 5Oct 9Oct 12Oct 15Oct 18Oct 23
24°FOct 3Oct 9Oct 14Oct 17Oct 20Oct 22Oct 25Oct 28Nov 1
20°FOct 13Oct 18Oct 22Oct 26Oct 29Oct 31Nov 3Nov 6Nov 12
16°FOct 21Oct 28Nov 1Nov 3Nov 6Nov 9Nov 13Nov 17Nov 22

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°F13813212712312011511110799
32°F160154149145142138134129122
28°F181174170166162158154149142
24°F203197193188183179175170163
20°F228221215210206202197191184
16°F249242236231226221216211202

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
7,736
Cooling degree days, base 65°F
453
Growing degree days, base 40°F
4,085
Growing degree days, base 45°F
3,069
Growing degree days, base 50°F
2,207
Growing degree days, base 55°F
1,491
Growing degree days, base 60°F
903

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42100
February1,14500
March89506
April611038
May33810185
June10370420
July17204652
August35145576
September21524280
October614049
November98602
December1,35800

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 9.3 km from Byron. 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 USC00485770 (Lovell). Public domain.