Bridgeport Frost Dates and Growing Season

NOAA 1991-2020 normals for Bridgeport, 0.3 km from Bridgeport, elevation 6470 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bridgeport. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

NOAA does not state freeze dates for this station.

Median at 28°F: last June 3, first September 15

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Jun 23	Jun 14	Jun 9	Jun 6	Jun 3	May 31	May 28	May 24	May 17
24°F	Jun 7	Jun 1	May 29	May 24	May 20	May 17	May 12	May 8	May 2
20°F	May 28	May 18	May 12	May 7	May 3	Apr 30	Apr 28	Apr 24	Apr 18
16°F	May 10	May 2	Apr 28	Apr 25	Apr 20	Apr 16	Apr 12	Apr 7	Mar 31

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Aug 30	Sep 4	Sep 7	Sep 12	Sep 15	Sep 18	Sep 22	Sep 26	Oct 1
24°F	Sep 15	Sep 20	Sep 23	Sep 27	Oct 1	Oct 2	Oct 5	Oct 8	Oct 13
20°F	Sep 28	Oct 3	Oct 5	Oct 8	Oct 12	Oct 14	Oct 17	Oct 22	Oct 27
16°F	Oct 8	Oct 13	Oct 17	Oct 20	Oct 24	Oct 27	Oct 30	Nov 2	Nov 5

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	59	50	44	39	35	30	27	23	18
32°F	94	87	81	75	69	63	57	49	42
28°F	125	117	112	106	102	97	92	86	76
24°F	154	146	141	136	132	127	122	117	108
20°F	182	174	168	163	159	154	148	142	133
16°F	211	203	197	191	186	180	174	167	159

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: 7,567
Cooling degree days, base 65°F: 68
Growing degree days, base 40°F: 3,156
Growing degree days, base 45°F: 2,162
Growing degree days, base 50°F: 1,372
Growing degree days, base 55°F: 747
Growing degree days, base 60°F: 299

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,186	0	0
February	1,002	0	0
March	890	0	1
April	690	0	11
May	488	0	80
June	227	6	245
July	67	41	439
August	104	19	380
September	282	1	187
October	611	0	29
November	875	0	1
December	1,145	0	1

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 0.3 km from Bridgeport. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00041072 (Bridgeport). Public domain.