Rolla climate

Rolla Frost Dates and Growing Season

NOAA 1991-2020 normals for Rolla 1NE, 3.5 km from Rolla, elevation 1833 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rolla 1NE. 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 20 and the first fall freeze around September 26, a growing season of about 128 days.

Median at 36°F
last May 29, first September 18
Median at 32°F
last May 20, first September 26
Median at 28°F
last May 11, first October 3

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 10Jun 5Jun 2May 31May 29May 26May 24May 21May 18
32°FMay 31May 28May 25May 22May 20May 18May 15May 13May 8
28°FMay 24May 19May 16May 13May 11May 8May 5May 3Apr 30
24°FMay 16May 11May 6May 4May 1Apr 30Apr 25Apr 21Apr 16
20°FMay 6May 2Apr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 8
16°FApr 30Apr 24Apr 19Apr 16Apr 14Apr 11Apr 8Apr 5Apr 2

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 5Sep 10Sep 13Sep 16Sep 18Sep 20Sep 22Sep 25Sep 28
32°FSep 14Sep 19Sep 21Sep 24Sep 26Sep 28Sep 30Oct 2Oct 8
28°FSep 21Sep 26Sep 28Oct 1Oct 3Oct 6Oct 10Oct 13Oct 18
24°FSep 29Oct 3Oct 7Oct 10Oct 13Oct 16Oct 19Oct 22Oct 27
20°FOct 8Oct 13Oct 16Oct 19Oct 23Oct 25Oct 28Nov 1Nov 6
16°FOct 16Oct 21Oct 25Oct 29Nov 1Nov 3Nov 6Nov 9Nov 14

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°F1281221181141111071039993
32°F145139135132128125121116111
28°F163158153150146143139134128
24°F182176172166163160156151144
20°F201194189185182177173167161
16°F217211206202198194190184176

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
10,496
Cooling degree days, base 65°F
156
Growing degree days, base 40°F
3,046
Growing degree days, base 45°F
2,210
Growing degree days, base 50°F
1,485
Growing degree days, base 55°F
890
Growing degree days, base 60°F
439

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,83200
February1,56000
March1,37200
April863015
May4724116
June18527302
July8363445
August10852411
September3449169
October785126
November1,22701
December1,66600

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 3.5 km from Rolla. 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 USC00327664 (Rolla 1NE). Public domain.