Last spring frost
Apr 7
Frost Dates for New Castle, DE
First fall frost
Nov 1
Growing season
209 days
Hardiness zone
7b
In an average year around New Castle, DE, the last spring frost (32°F) is about Apr 7 and the first fall frost is about Nov 1, giving roughly a 209-day growing season. To be safe most years, wait until Mar 26 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | May 7 | Apr 21 | Apr 7 |
| Freeze (32°F) | Apr 21 | Apr 7 | Mar 26 |
| Hard (28°F) | Apr 9 | Mar 27 | Mar 11 |
| Severe (24°F) | Mar 29 | Mar 15 | Feb 27 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 7 | May 1 | Apr 27 | Apr 23 | Apr 21 | Apr 18 | Apr 16 | Apr 12 | Apr 7 |
| 32°F | Apr 21 | Apr 16 | Apr 12 | Apr 10 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 26 |
| 28°F | Apr 9 | Apr 4 | Apr 1 | Mar 31 | Mar 27 | Mar 24 | Mar 20 | Mar 17 | Mar 11 |
| 24°F | Mar 29 | Mar 24 | Mar 21 | Mar 18 | Mar 15 | Mar 12 | Mar 9 | Mar 4 | Feb 27 |
| 20°F | Mar 19 | Mar 14 | Mar 10 | Mar 7 | Mar 4 | Mar 1 | Feb 25 | Feb 19 | Feb 12 |
| 16°F | Mar 10 | Mar 4 | Feb 28 | Feb 23 | Feb 18 | Feb 13 | Feb 8 | Feb 4 | Jan 27 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Oct 8 | Oct 22 | Nov 3 |
| Freeze (32°F) | Oct 19 | Nov 1 | Nov 15 |
| Hard (28°F) | Nov 1 | Nov 14 | Dec 1 |
| Severe (24°F) | Nov 11 | Nov 28 | Dec 16 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 8 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 24 | Oct 27 | Oct 31 | Nov 3 |
| 32°F | Oct 19 | Oct 24 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 15 |
| 28°F | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 14 | Nov 16 | Nov 20 | Nov 25 | Dec 1 |
| 24°F | Nov 11 | Nov 15 | Nov 20 | Nov 24 | Nov 28 | Dec 1 | Dec 4 | Dec 8 | Dec 16 |
| 20°F | Nov 22 | Nov 30 | Dec 4 | Dec 8 | Dec 13 | Dec 18 | Dec 22 | Dec 28 | Jan 4 |
| 16°F | Dec 7 | Dec 14 | Dec 22 | Dec 28 | Jan 1 | Jan 4 | Jan 9 | Jan 15 | Jan 25 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Wilmington New Castle Co Ap, De, about 1.9 miles away@if(!empty($station['elevation_ft'])), at 79 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in New Castle, DE?
On average, the last spring frost (32°F) around New Castle, DE is about Apr 7. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 26.
When is the first frost in the fall?
The first fall frost around New Castle, DE typically arrives about Nov 1. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Apr 7 on average, or Mar 26 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 209 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 19720 Planting calendar → Delaware frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026