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Will it freeze in Derby in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Wed, Nov 11: 32°F (Wed, Nov 11, 6:00 PM EST to Thu, Nov 12, 6:00 AM EST).
Tonight: forecast low 60°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM EST to Fri, Nov 6, 6:00 AM EST.
2 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 60°F Above 36°F · Light Rain
- Fri, Nov 6 52°F Above 36°F · Light Rain
- Sat, Nov 7 42°F Above 36°F · Chance Light Rain
- Sun, Nov 8 38°F Above 36°F · Mostly Clear
- Mon, Nov 9 36°F Frost possible · Mostly Clear
- Tue, Nov 10 37°F Above 36°F · Mostly Clear
- Wed, Nov 11 32°F Freeze · Partly Cloudy
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in Derby
The median first fall hard-freeze date (28°F) is October 30, from NOAA’s 1991–2020 Climate Normals at Ansonia 1 NE. This is the 50% probability date, not a forecast for this year.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | Apr 24 · May 8 · May 22 | Sep 27 · Oct 7 · Oct 21 | 151 days |
| 32°F freeze | Apr 11 · Apr 25 · May 10 | Oct 4 · Oct 17 · Nov 1 | 175 days |
| 28°F hard freeze | Mar 30 · Apr 10 · Apr 27 | Oct 14 · Oct 30 · Nov 13 | 202 days |
Average high temperature by month
1991–2020 normals at Ansonia 1 NE
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for Derby, CT come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Ansonia 1 NE (station USC00060128, elevation 136 ft), 1.7 mi from Derby. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near Derby
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Ansonia, CT | 1.2 mi | Apr 25 | Oct 17 |
| Shelton, CT | 3.1 mi | Apr 25 | Oct 17 |
| West Haven, CT | 6.8 mi | Apr 17 | Oct 27 |
| Milford, CT | 6.8 mi | Apr 5 | Nov 6 |
| New Haven, CT | 8.1 mi | Apr 17 | Oct 27 |
| Bridgeport, CT | 11 mi | Apr 5 | Nov 6 |
| Naugatuck, CT | 11 mi | Apr 18 | Oct 26 |
| Waterbury, CT | 16 mi | Apr 26 | Oct 16 |
| Meriden, CT | 21 mi | Apr 26 | Oct 16 |
| Danbury, CT | 21 mi | May 1 | Oct 14 |
Frequently asked questions
When is the last frost in Derby?
On average, the last spring frost (32°F) in Derby is around April 25. In about 1 year in 10 it comes after May 10, and in 9 years in 10 it comes after April 11.
When is the first frost in Derby?
The first fall frost (32°F) usually arrives around October 17. There’s a 10% chance of a freeze by October 4 and a 90% chance by November 1.
Can it frost in Derby after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after May 8.
What growing zone is Derby?
Derby is in USDA Plant Hardiness Zone 6b (average annual extreme minimum temperature −5 to 0°F), based on the 2023 USDA map for ZIP code 06418. See growing zones in Connecticut.
More: all Connecticut frost dates · Connecticut growing zones · frost vs. freeze