Brooklyn climate

Brooklyn Frost Dates and Growing Season

NOAA 1991-2020 normals for Belle Plaine, 21.5 km from Brooklyn, elevation 810 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Belle Plaine. 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 28 and the first fall freeze around October 10, a growing season of about 165 days.

Median at 36°F
last May 6, first October 1
Median at 32°F
last April 28, first October 10
Median at 28°F
last April 16, first October 21

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 20May 15May 11May 8May 6May 3May 1Apr 28Apr 24
32°FMay 11May 7May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 14
28°FMay 2Apr 27Apr 23Apr 19Apr 16Apr 13Apr 10Apr 7Apr 2
24°FApr 23Apr 16Apr 12Apr 9Apr 5Apr 3Mar 31Mar 28Mar 21
20°FApr 11Apr 5Apr 2Mar 31Mar 28Mar 24Mar 20Mar 15Mar 9
16°FApr 1Mar 27Mar 23Mar 20Mar 16Mar 12Mar 9Mar 5Mar 1

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 17Sep 22Sep 26Sep 29Oct 1Oct 3Oct 5Oct 9Oct 13
32°FSep 26Oct 1Oct 4Oct 7Oct 10Oct 13Oct 15Oct 18Oct 23
28°FOct 5Oct 11Oct 15Oct 18Oct 21Oct 23Oct 25Oct 28Nov 1
24°FOct 17Oct 22Oct 25Oct 28Oct 30Nov 1Nov 3Nov 6Nov 12
20°FOct 28Nov 1Nov 2Nov 5Nov 7Nov 10Nov 14Nov 18Nov 25
16°FNov 3Nov 8Nov 11Nov 15Nov 17Nov 21Nov 25Nov 29Dec 4

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°F165158154150147143139135128
32°F185177172168165161157151145
28°F206199193189185181176171165
24°F226219214210207203197192185
20°F249241236231227222219214205
16°F267261256251246242238232224

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
6,868
Cooling degree days, base 65°F
785
Growing degree days, base 40°F
5,065
Growing degree days, base 45°F
3,968
Growing degree days, base 50°F
2,989
Growing degree days, base 55°F
2,129
Growing degree days, base 60°F
1,391

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,41800
February1,16101
March903123
April498497
May20249327
June27177600
July5261721
August13203656
September12679408
October44610138
November836017
December1,23401

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 21.5 km from Brooklyn. 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 USC00130600 (Belle Plaine). Public domain.