Ellicott climate

Ellicott Frost Dates and Growing Season

NOAA 1991-2020 normals for Ellicott 7S, 10.9 km from Ellicott, elevation 5739 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ellicott 7S. 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 6 and the first fall freeze around October 3, a growing season of about 149 days.

Median at 36°F
last May 19, first September 25
Median at 32°F
last May 6, first October 3
Median at 28°F
last April 25, first October 12

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 9Jun 2May 29May 24May 19May 15May 12May 8May 3
32°FMay 28May 19May 13May 10May 6May 3Apr 30Apr 26Apr 21
28°FMay 12May 6May 1Apr 29Apr 25Apr 22Apr 18Apr 14Apr 8
24°FMay 2Apr 26Apr 21Apr 18Apr 13Apr 9Apr 5Apr 1Mar 25
20°FApr 21Apr 14Apr 9Apr 5Apr 1Mar 29Mar 25Mar 19Mar 13
16°FApr 9Apr 3Mar 30Mar 25Mar 20Mar 16Mar 11Mar 7Feb 28

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 13Sep 17Sep 19Sep 22Sep 25Sep 27Sep 30Oct 3Oct 6
32°FSep 21Sep 26Sep 29Oct 1Oct 3Oct 5Oct 8Oct 11Oct 16
28°FSep 29Oct 3Oct 6Oct 9Oct 12Oct 14Oct 17Oct 20Oct 26
24°FOct 9Oct 13Oct 16Oct 19Oct 21Oct 25Oct 28Nov 1Nov 5
20°FOct 16Oct 20Oct 24Oct 28Oct 31Nov 2Nov 5Nov 9Nov 15
16°FOct 21Oct 27Nov 1Nov 4Nov 8Nov 11Nov 14Nov 19Nov 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°F150143137132127123117111103
32°F168162157153149145141133126
28°F190183178173169165160155148
24°F213206199195190185180174167
20°F236226221216211206201195188
16°F256247241235230225220213204

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
5,773
Cooling degree days, base 65°F
581
Growing degree days, base 40°F
5,008
Growing degree days, base 45°F
3,807
Growing degree days, base 50°F
2,769
Growing degree days, base 55°F
1,886
Growing degree days, base 60°F
1,156

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,07100
February86708
March716027
April4622101
May21734306
June5494490
July7204661
August11191644
September12952380
October4504129
November758020
December1,03103

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 10.9 km from Ellicott. 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 USC00052668 (Ellicott 7S). Public domain.