US Grow Zones

Stamford, Connecticut: planting zone & frost dates

Last updated · Sources: PRISM/OSU 2023 ZIP zone listings; NOAA NCEI 1991–2020 Climate Normals (station USC00067970); U.S. Census Bureau — see methodology

Stamford is in USDA plant hardiness zone 7a, where the average coldest winter night reaches 0 to 5°F (-17.8 to -15.0°C). The typical last spring frost is around Apr 23 and the first fall frost around Oct 16.

Hardiness zone7A0 to 5°F
Last spring frostApr 2330% chance of frost after
First fall frostOct 1630% chance of frost before
Growing season188 daysmedian frost-free days

Frost dates

ProbabilityLast spring frost (32°F)First fall frost (32°F)
Safer (10% risk)May 2Oct 8
Typical planning date (30% risk)Apr 23Oct 16
Median (50%)Apr 17Oct 23

How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.

Frost data comes from NOAA station STAMFORD 5 N, CT (USC00067970), 3.1 mi (5.0 km) from the city center and 43 ft higher than the city center (+13 m). Record used for the 1991–2020 normals: 22 years.

Frost probability in spring and fall, Stamford, CTChance of a 32°F frost in Stamford, CT, NOAA 1991–2020. Spring: the chance of another frost falls from 90% on Apr 3 to 10% on May 2. Fall: the chance that the first frost has arrived rises from 10% on Oct 8 to 90% on Nov 6.0%50%100%Spring: later frostMar 15Apr 1Apr 15May 130%: Apr 23Fall: frost arrivedOct 1Oct 15Nov 1Nov 1530%: Oct 1632°F frost28°F hard freezeplanning date
Shaded areas show the chance of a 32°F frost: falling through spring, rising through fall. The dashed line is the 28°F hard-freeze curve. Data: NOAA 1991–2020 Normals, station USC00067970.
Frost-free growing season in Stamford, CT1 in 10 risk: May 2 to Oct 8 (159 days); 3 in 10 risk: Apr 23 to Oct 16 (176 days); Median (50%): Apr 17 to Oct 23 (189 days); No 28°F freeze: Apr 3 to Nov 2 (213 days). In 9 of 10 years the 32°F-free season is at least 168 days.Frost-free days, spring to fallJFMAMJJASOND1 in 10 risk159 days3 in 10 risk176 daysMedian (50%)189 daysNo 28°F freeze213 days
Frost-free window at three risk levels, plus the window between 28°F hard freezes. Read about what the probabilities mean.

Why your yard may differ from the station: microclimates.

Hardiness zone across Stamford

All 7 ZIP codes covering Stamford are in zone 7a.

ZIP codes in Stamford and their zones
ZIPZoneShare of city land
069037a46.2%
069027a26.6%
069057a13.5%
069077a5.2%
069067a3.6%
068317a3.5%
069017a1.4%

Vegetable planting calendar for Stamford

Dates are counted from the 30%-risk frost dates above (last frost Apr 23, first frost Oct 16). Shift a week later in cold spots or low-lying ground.

CropStart indoorsTransplant / plant outDirect sowFall crop sow/plant
TomatoFeb 26 – Mar 12Apr 30 – May 14——
PepperFeb 12 – Feb 26May 7 – May 21——
LettuceMar 12 – Mar 26Apr 9 – Apr 30Mar 26 – May 7Aug 7 – Sep 4
Green Beans——Apr 30 – Jun 4Jul 24 – Aug 7
Sweet Corn——Apr 30 – May 28—
Zucchini & Summer SquashMar 26 – Apr 2Apr 30 – May 14Apr 30 – May 21Jul 24 – Aug 7
CucumberMar 26 – Apr 2May 7 – May 14Apr 30 – May 21Jul 24 – Aug 7
Carrot——Apr 2 – May 7Jul 24 – Aug 7
OnionJan 29 – Feb 12Mar 26 – Apr 9——
Potato—Mar 26 – Apr 16——
BasilMar 12 – Mar 26May 7 – May 21May 7 – May 28—
Spinach——Mar 12 – Apr 9Aug 21 – Sep 18
KaleFeb 26 – Mar 12Mar 26 – Apr 16Mar 26 – Apr 16Aug 7 – Sep 4
BroccoliFeb 26 – Mar 12Apr 9 – Apr 30—Jul 24 – Aug 7
Peas——Mar 12 – Apr 2Aug 7 – Aug 21
EggplantFeb 12 – Feb 26May 7 – May 21——
CabbageFeb 26 – Mar 12Mar 26 – Apr 9—Jul 24 – Aug 7
Radish——Mar 19 – May 7Sep 4 – Oct 2
Strawberry—Mar 26 – Apr 16——
Beets——Apr 2 – May 14Aug 7 – Aug 21

Nearby cities in Connecticut

More: all Connecticut cities · other zone 7a cities: Louisville, KY, Wichita, KS, Cleveland, OH, Lexington, KY, St. Louis, MO, Boise, ID, Amarillo, TX, Providence, RI

Stamford gardening questions

When is the last frost in Stamford, CT?

Plan around Apr 23. At NOAA's Stamford 5 N, CT station, 3.1 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 17, and after May 2 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 3. The 90% and 10% dates are 29 days apart, close to the 36-day median for cities on this site.

When should I plant tomatoes in Stamford, CT?

Start seeds indoors Feb 26 – Mar 12 and set transplants outside Apr 30 – May 14, once nights stay above 50°F and the soil is near 60°F. That leaves 176 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.

How long is the growing season in Stamford?

About 188 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 168 days, and in 1 year in 10 it runs 208 days or more. In fall there is a 10% chance of frost by Oct 8 and a 30% chance by Oct 16. That ranks 4th longest of 7 Connecticut cities on this site.

When should I plant a fall garden in Stamford?

Count back from the first fall frost (Oct 16): transplant broccoli Jul 24 – Aug 7; sow kale Aug 7 – Sep 4; sow lettuce Aug 7 – Sep 4; sow radishes Sep 4 – Oct 2. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 2. How the math works: succession and fall planting.

Did Stamford's hardiness zone change on the 2023 map?

Yes. Most of Stamford was zone 6b on the 2012 map and is zone 7a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.

How does Stamford compare with New Rochelle, NY?

Stamford is zone 7a and New Rochelle is zone 7b. The typical last spring frost in Stamford (Apr 23) comes about 18 days later than in New Rochelle, NY (Apr 5), 16 miles away, and the first fall frost is Oct 16 versus Nov 9. The two cities use different NOAA stations.