Marlborough, CT frost dates
Last spring frostApr 17median date
First fall frostOct 26median date
Growing season192 daysfrost-free
Hardiness zone6bZone 6b
How Marlborough compares
- In 8 years out of 10, the last spring frost in Marlborough falls between April 1 and May 1, a 30-day window. The first fall frost falls between October 12 and November 7.
- The median last frost is 4 days earlier than the Connecticut median of Apr 21.
- Its 192-day growing season is longer than 70% of the 267 Connecticut places with a regular frost season (state median 178 days).
- The last frost is 5 days earlier than the zone 6b median of Apr 22. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6b chart.
- The weather station records an average of 121 nights a year at or below 32°F.
- Marlborough shares its weather station with East Hartford, CT, 23 km away, so the two have the same frost dates.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 1 |
| 50% (median) | April 17 |
| 10% (safe for tender plants) | May 1 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 12 |
| 50% (median) | October 26 |
| 90% (late) | November 7 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Marlborough, CT
Marlborough, CT frost dates — last frost Apr 17, first frost Oct 26, zone 6b. whenisthelastfrost.com
Crop
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Start indoors: Jan 23 to Feb 6Transplant outside: Mar 20 to Apr 3
Start indoors: Feb 6 to Feb 20Transplant outside: May 1 to May 15
Start indoors: Feb 6 to Feb 20Transplant outside: May 1 to May 15
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 24 to May 8
Start indoors: Feb 20 to Mar 6Transplant outside: Mar 27 to Apr 10Sow outdoors: Mar 20 to Apr 24Plant for fall: Aug 31 to Sep 28
Start indoors: Feb 20 to Mar 6Transplant outside: Mar 20 to Apr 3Sow outdoors: Mar 20 to Apr 3Plant for fall: Aug 17 to Sep 7
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 3 to Apr 17Plant for fall: Jul 20 to Aug 10
Start indoors: Feb 20 to Mar 6Transplant outside: Mar 27 to Apr 10Plant for fall: Jul 20 to Aug 10
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 3 to Apr 17Plant for fall: Jul 20 to Aug 10
Start indoors: Mar 6 to Mar 20Transplant outside: May 8 to May 22Sow outdoors: May 8 to May 22
Start indoors: Mar 6 to Mar 20Transplant outside: Apr 24 to May 8
Sow outdoors: Mar 6 to Mar 27Plant for fall: Aug 3 to Aug 24
Sow outdoors: Mar 6 to Mar 27Plant for fall: Aug 31 to Sep 21
Sow outdoors: Mar 13 to Apr 24Plant for fall: Sep 14 to Oct 5
Start indoors: Mar 20 to Mar 27Transplant outside: May 1 to May 8Sow outdoors: Apr 24 to May 8Plant for fall: Aug 10 to Aug 24
Start indoors: Mar 20 to Mar 27Sow outdoors: Apr 24 to May 8Plant for fall: Aug 17 to Aug 31
Start indoors: Mar 20 to Mar 27Sow outdoors: Apr 24 to May 8
Start indoors: Mar 20 to Mar 27Transplant outside: May 1 to May 15
Sow outdoors: Mar 27 to Apr 24Plant for fall: Aug 3 to Aug 17
Sow outdoors: Mar 27 to Apr 24Plant for fall: Aug 17 to Aug 31
Sow outdoors: Mar 27 to Apr 17
Sow outdoors: Apr 3 to May 1Plant for fall: Aug 17 to Aug 31
Sow outdoors: Apr 3 to Apr 24Plant for fall: Aug 31 to Sep 21
Sow outdoors: Apr 24 to May 15Plant for fall: Aug 10 to Aug 24
Sow outdoors: Apr 24 to May 8
Transplant outside: May 1 to May 22
Plant for fall: Oct 12 to Nov 16
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Marlborough, CT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 23 – Feb 6 | Mar 20 – Apr 3 | — | — |
| Peppers | Feb 6 – Feb 20 | May 1 – May 15 | — | — |
| Eggplant | Feb 6 – Feb 20 | May 1 – May 15 | — | — |
| Tomatoes | Feb 20 – Mar 6 | Apr 24 – May 8 | — | — |
| Lettuce | Feb 20 – Mar 6 | Mar 27 – Apr 10 | Mar 20 – Apr 24 | Aug 31 – Sep 28 |
| Kale | Feb 20 – Mar 6 | Mar 20 – Apr 3 | Mar 20 – Apr 3 | Aug 17 – Sep 7 |
| Broccoli | Feb 20 – Mar 6 | Apr 3 – Apr 17 | — | Jul 20 – Aug 10 |
| Cabbage | Feb 20 – Mar 6 | Mar 27 – Apr 10 | — | Jul 20 – Aug 10 |
| Cauliflower | Feb 20 – Mar 6 | Apr 3 – Apr 17 | — | Jul 20 – Aug 10 |
| Okra | Mar 6 – Mar 20 | May 8 – May 22 | May 8 – May 22 | — |
| Basil | Mar 6 – Mar 20 | Apr 24 – May 8 | — | — |
| Peas | — | — | Mar 6 – Mar 27 | Aug 3 – Aug 24 |
| Spinach | — | — | Mar 6 – Mar 27 | Aug 31 – Sep 21 |
| Radishes | — | — | Mar 13 – Apr 24 | Sep 14 – Oct 5 |
| Cucumbers | Mar 20 – Mar 27 | May 1 – May 8 | Apr 24 – May 8 | Aug 10 – Aug 24 |
| Zucchini & Summer Squash | Mar 20 – Mar 27 | — | Apr 24 – May 8 | Aug 17 – Aug 31 |
| Winter Squash & Pumpkins | Mar 20 – Mar 27 | — | Apr 24 – May 8 | — |
| Melons & Watermelon | Mar 20 – Mar 27 | May 1 – May 15 | — | — |
| Carrots | — | — | Mar 27 – Apr 24 | Aug 3 – Aug 17 |
| Beets | — | — | Mar 27 – Apr 24 | Aug 17 – Aug 31 |
| Potatoes | — | — | Mar 27 – Apr 17 | — |
| Swiss Chard | — | — | Apr 3 – May 1 | Aug 17 – Aug 31 |
| Cilantro | — | — | Apr 3 – Apr 24 | Aug 31 – Sep 21 |
| Green Beans | — | — | Apr 24 – May 15 | Aug 10 – Aug 24 |
| Sweet Corn | — | — | Apr 24 – May 8 | — |
| Sweet Potatoes | — | May 1 – May 22 | — | — |
| Garlic | — | — | — | Oct 12 – Nov 16 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Hartford Brainard Fld, CT weather station, 19 km away (elevation 20 ft (6 m)).
Frost dates near Marlborough
- Hebron Apr 19 · Oct 22
- East Glastonbury Apr 17 · Oct 26
- Amston Apr 28 · Oct 13
- East Hampton Apr 17 · Oct 26
- North Westchester Apr 28 · Oct 13
- South Glastonbury Apr 17 · Oct 26
- Cobalt Apr 17 · Oct 26
- Glastonbury Apr 17 · Oct 26
- Middle Haddam Apr 17 · Oct 26
- Andover Apr 19 · Oct 22
Frequently asked questions
When is the last frost in Marlborough, CT?
The median last spring frost in Marlborough, CT is April 17. There is still about a 10% chance of frost after May 1, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Marlborough, CT?
The median first fall frost is October 26, with about a 10% chance of frost before October 12.
How long is the growing season in Marlborough, CT?
About 192 days between the median last spring frost and first fall frost.
What planting zone is Marlborough, CT?
Marlborough, CT is in USDA hardiness zone 6b.