Poplar climate

Poplar Frost Dates and Growing Season

NOAA 1991-2020 normals for Brule RS, 16.6 km from Poplar, elevation 1000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Brule RS. 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 24 and the first fall freeze around September 26, a growing season of about 124 days.

Median at 36°F
last June 5, first September 14
Median at 32°F
last May 24, first September 26
Median at 28°F
last May 9, first October 6

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 21Jun 14Jun 10Jun 7Jun 5Jun 2May 30May 27May 22
32°FJun 6Jun 2May 30May 27May 24May 21May 18May 14May 8
28°FMay 27May 20May 16May 13May 9May 6May 2Apr 30Apr 26
24°FMay 12May 7May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 13
20°FApr 29Apr 24Apr 21Apr 18Apr 15Apr 13Apr 9Apr 6Apr 2
16°FApr 22Apr 16Apr 11Apr 8Apr 5Apr 3Apr 1Mar 29Mar 24

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 30Sep 3Sep 7Sep 11Sep 14Sep 17Sep 20Sep 24Sep 29
32°FSep 9Sep 15Sep 19Sep 23Sep 26Sep 29Oct 1Oct 4Oct 9
28°FSep 20Sep 26Oct 1Oct 3Oct 6Oct 10Oct 13Oct 17Oct 24
24°FOct 3Oct 9Oct 13Oct 17Oct 21Oct 24Oct 27Nov 1Nov 4
20°FOct 18Oct 24Oct 28Oct 31Nov 2Nov 5Nov 8Nov 11Nov 16
16°FOct 31Nov 2Nov 5Nov 8Nov 11Nov 13Nov 16Nov 20Nov 24

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°F1201131081049995908476
32°F146139133128124120115110103
28°F172164158153149146141135127
24°F195188183178175170165160152
20°F219212207202198194190184177
16°F237230225221217214210205198

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
9,112
Cooling degree days, base 65°F
245
Growing degree days, base 40°F
3,440
Growing degree days, base 45°F
2,536
Growing degree days, base 50°F
1,755
Growing degree days, base 55°F
1,095
Growing degree days, base 60°F
582

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,67400
February1,38600
March1,16403
April762120
May41111144
June14843349
July57103511
August8268452
September27520228
October655145
November1,03404
December1,46600

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 16.6 km from Poplar. 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 USC00471131 (Brule RS). Public domain.