Waterbury, Connecticut: planting zone & frost dates
Waterbury 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 May 1 and the first fall frost around Oct 11.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 9 | Oct 4 |
| Typical planning date (30% risk) | May 1 | Oct 11 |
| Median (50%) | Apr 26 | Oct 16 |
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 MERIDEN MARKHAM MUNI AP, CT (USW00054788), 11.3 mi (18.2 km) from the city center and 230 ft lower than the city center (-70 m). Record used for the 1991–2020 normals: 19 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Waterbury
All 6 ZIP codes covering Waterbury are in zone 6b.
Vegetable planting calendar for Waterbury
Dates are counted from the 30%-risk frost dates above (last frost May 1, first frost Oct 11). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 6 – Mar 20 | May 8 – May 22 | — | — |
| Pepper | Feb 20 – Mar 6 | May 15 – May 29 | — | — |
| Lettuce | Mar 20 – Apr 3 | Apr 17 – May 8 | Apr 3 – May 15 | Aug 2 – Aug 30 |
| Green Beans | — | — | May 8 – Jun 12 | Jul 19 – Aug 2 |
| Sweet Corn | — | — | May 8 – Jun 5 | — |
| Zucchini & Summer Squash | Apr 3 – Apr 10 | May 8 – May 22 | May 8 – May 29 | Jul 19 – Aug 2 |
| Cucumber | Apr 3 – Apr 10 | May 15 – May 22 | May 8 – May 29 | Jul 19 – Aug 2 |
| Carrot | — | — | Apr 10 – May 15 | Jul 19 – Aug 2 |
| Onion | Feb 6 – Feb 20 | Apr 3 – Apr 17 | — | — |
| Potato | — | Apr 3 – Apr 24 | — | — |
| Basil | Mar 20 – Apr 3 | May 15 – May 29 | May 15 – Jun 5 | — |
| Spinach | — | — | Mar 20 – Apr 17 | Aug 16 – Sep 13 |
| Kale | Mar 6 – Mar 20 | Apr 3 – Apr 24 | Apr 3 – Apr 24 | Aug 2 – Aug 30 |
| Broccoli | Mar 6 – Mar 20 | Apr 17 – May 8 | — | Jul 19 – Aug 2 |
| Peas | — | — | Mar 20 – Apr 10 | Aug 2 – Aug 16 |
| Eggplant | Feb 20 – Mar 6 | May 15 – May 29 | — | — |
| Cabbage | Mar 6 – Mar 20 | Apr 3 – Apr 17 | — | Jul 19 – Aug 2 |
| Radish | — | — | Mar 27 – May 15 | Aug 30 – Sep 27 |
| Strawberry | — | Apr 3 – Apr 24 | — | — |
| Beets | — | — | Apr 10 – May 22 | Aug 2 – Aug 16 |
Nearby cities in Connecticut
- New Haven — zone 7a, last frost Apr 22, first frost Oct 20
- Bridgeport — zone 7a, last frost Apr 9, first frost Nov 1
- Hartford — zone 6b, last frost Apr 23, first frost Oct 20
- 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
Waterbury gardening questions
When is the last frost in Waterbury, CT?
Plan around May 1. At NOAA's Meriden Markham Municipal Airport, CT station, 11.3 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 26, and after May 9 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 10. The last frost is fairly predictable here: only 28 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Waterbury, CT?
Start seeds indoors Mar 6 – Mar 20 and set transplants outside May 8 – May 22, once nights stay above 50°F and the soil is near 60°F. That leaves 163 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 Waterbury?
About 175 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 156 days, and in 1 year in 10 it runs 194 days or more. In fall there is a 10% chance of frost by Oct 4 and a 30% chance by Oct 11. That ranks 6th longest of 7 Connecticut cities on this site.
When should I plant a fall garden in Waterbury?
Count back from the first fall frost (Oct 11): transplant broccoli Jul 19 – Aug 2; sow kale Aug 2 – Aug 30; sow lettuce Aug 2 – Aug 30; sow radishes Aug 30 – Sep 27. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 30. How the math works: succession and fall planting.
Did Waterbury's hardiness zone change on the 2023 map?
Yes. Most of Waterbury was zone 6a on the 2012 map and is zone 6b 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 Waterbury compare with New Haven, CT?
Waterbury is zone 6b and New Haven is zone 7a. The typical last spring frost in Waterbury (May 1) comes about 9 days later than in New Haven, CT (Apr 22), 18 miles away, and the first fall frost is Oct 11 versus Oct 20. Waterbury sits about 303 ft higher, which explains part of the gap. The two cities use different NOAA stations.