USDA Hardiness Zone 6b
Frost Dates for 06423 — East Haddam, Connecticut
NOAA 1991–2020 normals from Norwich Public Utility Plt, CT (20 ft), 18 miles east.
Updated
In East Haddam, the last spring frost (32°F) is around April 14 in half of years and has passed by April 30 in nine years out of ten. The first fall frost comes around October 24, as early as October 9 one year in ten, leaving a typical freeze-free season of 192 days (NOAA, Norwich Public Utility Plt, CT).
- Last spring frost
- April 14
- First fall frost
- October 24
- Growing season
- 192 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- December 10
- Last snow
- March 15
- Winters with snow
- 100%
- Snow per year
- 27.8"
median, 1991–2020
median, 1991–2020
25 of 25 observed
NOAA normal
Frost risk by date in East Haddam
Half of springs at Norwich Public Utility Plt, CT see their last 32°F night by April 14; only one in ten is past it by April 1, and one in ten still has one after April 30. Planting tender crops after April 21 leaves a 30% risk of a frost on them, after April 24 20%, and after April 30 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 82% of the 28 Connecticut stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 24 in half of years, as early as October 9 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 12 days later, around November 5; in spring the one-in-ten date for 28°F is April 16, 14 days before the 32°F one. The freeze-free season lasts 192 days in a typical year, longer than at 75% of the 28 Connecticut stations; it reaches 211 days one year in ten and falls short of 170 one year in ten. On average 124 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 16 days longer, to about April 30, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 16 and March 4.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 16 | Apr 20 | Apr 24 | Apr 27 | Apr 30 | May 2 | May 5 | May 8 | May 13 |
| 32°F | Apr 1 | Apr 6 | Apr 9 | Apr 11 | Apr 14 | Apr 18 | Apr 21 | Apr 24 | Apr 30 |
| 28°F | Mar 18 | Mar 25 | Mar 29 | Mar 31 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 16 |
| 24°F | Mar 6 | Mar 13 | Mar 16 | Mar 19 | Mar 23 | Mar 26 | Mar 29 | Mar 31 | Apr 3 |
| 20°F | Feb 26 | Mar 3 | Mar 6 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 24 | Mar 29 |
| 16°F | Feb 11 | Feb 20 | Feb 25 | Mar 1 | Mar 4 | Mar 7 | Mar 11 | Mar 15 | Mar 21 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 1 | Oct 3 | Oct 6 | Oct 8 | Oct 12 | Oct 15 | Oct 19 | Oct 23 | Oct 29 |
| 32°F | Oct 9 | Oct 13 | Oct 17 | Oct 20 | Oct 24 | Oct 27 | Oct 31 | Nov 3 | Nov 7 |
| 28°F | Oct 19 | Oct 26 | Oct 31 | Nov 2 | Nov 5 | Nov 7 | Nov 11 | Nov 14 | Nov 21 |
| 24°F | Nov 1 | Nov 8 | Nov 11 | Nov 14 | Nov 18 | Nov 22 | Nov 26 | Dec 1 | Dec 5 |
| 20°F | Nov 15 | Nov 21 | Nov 27 | Nov 30 | Dec 2 | Dec 6 | Dec 10 | Dec 15 | Dec 21 |
| 16°F | Nov 29 | Dec 3 | Dec 8 | Dec 12 | Dec 16 | Dec 21 | Dec 25 | Dec 30 | Jan 5 |
Freeze probabilities 1991–2020 at Norwich Public Utility Plt, CT, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 06423 →Compare East Haddam with another place →
Weather by month in East Haddam
July is the warmest month at Norwich Public Utility Plt, CT, averaging 84°F by day and 65°F at night; January is the coldest at 38°F and 21°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 3,066 growing degree days a year (base 50°F), more than at 71% of the 28 Connecticut stations. 31% of them (945) have built up by the end of June, and July adds the most, 758. Precipitation totals 52.3 inches a year, most in March (5.1") and least in May (3.6"); May to September bring 40% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 38 | 21 | 3.9 | 100% | 27 | 1 |
| Feb | 41 | 23 | 3.8 | 100% | 24 | 1 |
| Mar | 48 | 29 | 5.1 | 100% | 22 | 12 |
| Apr | 59 | 39 | 4.7 | 92% | 7 | 80 |
| May | 70 | 49 | 3.6 | 8% | <1 | 297 |
| Jun | 78 | 59 | 4.3 | 0% | 0 | 554 |
| Jul | 84 | 65 | 3.6 | 0% | 0 | 758 |
| Aug | 83 | 63 | 4.4 | 0% | 0 | 702 |
| Sep | 76 | 55 | 4.8 | 1% | <1 | 457 |
| Oct | 64 | 44 | 4.9 | 71% | 4 | 166 |
| Nov | 53 | 34 | 4.2 | 100% | 15 | 33 |
| Dec | 43 | 27 | 5.0 | 100% | 25 | 6 |
Monthly normals 1991–2020 at Norwich Public Utility Plt, CT (20 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Groton, CT, 21 miles southeast of East Haddam, has a last frost 6 days earlier (April 8), a first frost 9 days later (November 2), a season 15 days longer.
When it snows in East Haddam, Connecticut
The first measurable snow (0.1 inch or more) in East Haddam usually arrives around December 10, and the last of the season around March 15. Those are the middle dates across the winters of 1991–2020 at Norwich Public Utility Plt, CT, 18.1 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 30 days after the last snow.
Planting calendar for 06423
| When | What to do |
|---|---|
| February 3 – February 17 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 17 – March 3 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 17 – March 31 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 14 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 1 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 10 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 24 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 06423 is 18 miles from Norwich Public Utility Plt, CT, which stands at 20 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 12 other ZIP codes share the station; its figures are presented in full for 06360 (Norwich). The 2023 USDA Plant Hardiness Zone Map lists ZIP 06423 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Connecticut →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.