Hartford, Connecticut: planting zone & frost dates
Hartford is in USDA plant hardiness zone 6b, where the average coldest winter night reaches -5 to 0°F (-20.6 to -17.8°C). The typical last spring frost is around Apr 23 and the first fall frost around Oct 20.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 1 | Oct 12 |
| Typical planning date (30% risk) | Apr 23 | Oct 20 |
| Median (50%) | Apr 17 | Oct 26 |
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 HARTFORD BRAINARD FLD, CT (USW00014752), 2.6 mi (4.2 km) from the city center and 13 ft lower than the city center (-4 m). Record used for the 1991–2020 normals: 28 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Hartford
All 6 ZIP codes covering Hartford are in zone 6b.
Vegetable planting calendar for Hartford
Dates are counted from the 30%-risk frost dates above (last frost Apr 23, first frost Oct 20). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Feb 26 – Mar 12 | Apr 30 – May 14 | — | — |
| Pepper | Feb 12 – Feb 26 | May 7 – May 21 | — | — |
| Lettuce | Mar 12 – Mar 26 | Apr 9 – Apr 30 | Mar 26 – May 7 | Aug 11 – Sep 8 |
| Green Beans | — | — | Apr 30 – Jun 4 | Jul 28 – Aug 11 |
| Sweet Corn | — | — | Apr 30 – May 28 | — |
| Zucchini & Summer Squash | Mar 26 – Apr 2 | Apr 30 – May 14 | Apr 30 – May 21 | Jul 28 – Aug 11 |
| Cucumber | Mar 26 – Apr 2 | May 7 – May 14 | Apr 30 – May 21 | Jul 28 – Aug 11 |
| Carrot | — | — | Apr 2 – May 7 | Jul 28 – Aug 11 |
| Onion | Jan 29 – Feb 12 | Mar 26 – Apr 9 | — | — |
| Potato | — | Mar 26 – Apr 16 | — | — |
| Basil | Mar 12 – Mar 26 | May 7 – May 21 | May 7 – May 28 | — |
| Spinach | — | — | Mar 12 – Apr 9 | Aug 25 – Sep 22 |
| Kale | Feb 26 – Mar 12 | Mar 26 – Apr 16 | Mar 26 – Apr 16 | Aug 11 – Sep 8 |
| Broccoli | Feb 26 – Mar 12 | Apr 9 – Apr 30 | — | Jul 28 – Aug 11 |
| Peas | — | — | Mar 12 – Apr 2 | Aug 11 – Aug 25 |
| Eggplant | Feb 12 – Feb 26 | May 7 – May 21 | — | — |
| Cabbage | Feb 26 – Mar 12 | Mar 26 – Apr 9 | — | Jul 28 – Aug 11 |
| Radish | — | — | Mar 19 – May 7 | Sep 8 – Oct 6 |
| Strawberry | — | Mar 26 – Apr 16 | — | — |
| Beets | — | — | Apr 2 – May 14 | Aug 11 – Aug 25 |
Nearby cities in Connecticut
- Waterbury — zone 6b, last frost May 1, first frost Oct 11
- New Haven — zone 7a, last frost Apr 22, first frost Oct 20
- Bridgeport — zone 7a, last frost Apr 9, first frost Nov 1
- Danbury — zone 6b, last frost May 6, first frost Oct 7
- Norwalk — zone 7a, last frost Apr 23, first frost Oct 16
- Stamford — zone 7a, last frost Apr 23, first frost Oct 16
More: all Connecticut cities · other zone 6b cities: Columbus, OH, Indianapolis, IN, Boston, MA, Detroit, MI, Kansas City, MO, Cincinnati, OH, Pittsburgh, PA, Buffalo, NY
Hartford gardening questions
When is the last frost in Hartford, CT?
Plan around Apr 23. At NOAA's Hartford Brainard Field, CT station, 2.6 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 1 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 30 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Hartford, 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 180 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 Hartford?
About 191 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 169 days, and in 1 year in 10 it runs 212 days or more. In fall there is a 10% chance of frost by Oct 12 and a 30% chance by Oct 20. That ranks 3rd longest of 7 Connecticut cities on this site.
When should I plant a fall garden in Hartford?
Count back from the first fall frost (Oct 20): transplant broccoli Jul 28 – Aug 11; sow kale Aug 11 – Sep 8; sow lettuce Aug 11 – Sep 8; sow radishes Sep 8 – Oct 6. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 5. How the math works: succession and fall planting.
Did Hartford's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Hartford is zone 6b on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.
How does Hartford compare with Waterbury, CT?
Both are in zone 6b. The typical last spring frost in Hartford (Apr 23) comes about 8 days earlier than in Waterbury, CT (May 1), 23 miles away, and the first fall frost is Oct 20 versus Oct 11. Hartford sits about 299 ft lower, which explains part of the gap. The two cities use different NOAA stations.