White Harbor Labs › Frost Dates › States › Delaware
Frost Dates in Delaware
First and last frost dates across Delaware, computed from 6 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
Apr 6
statewide median · range Mar 29–Apr 7
First fall frost
Nov 4
statewide median · range Nov 1–Nov 14
Growing season
212 days
median · range 208–231
Stations used
6
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Wilmington | Wilmington Porter Rsch · 2 mi | Apr 7 (cautious: Apr 24) | Nov 4 | 209 days | Apr 21 |
| Dover | Dover · 1 mi | Apr 4 (cautious: Apr 17) | Nov 4 | 214 days | Apr 18 |
How frost varies across Delaware
Spring frost timing spans about 9 days across the state. Lewes in southern Delaware typically sees its last spring frost around March 29, while Newark Ag Farm in northern Delaware doesn't clear frost until about April 7. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Delaware
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around April 20 for the statewide median. Check your city's row above rather than the statewide median: a 9-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 6 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
More states
Frequently asked questions
When is the last frost date in Delaware?
The statewide median last spring frost is April 6, but it ranges from March 29 to April 7 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Delaware?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around April 20 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Delaware?
The median growing season across 6 NOAA stations is 212 days, ranging from 208 to 231 days by location.
Why do frost dates vary so much within Delaware?
Frost timing follows latitude, elevation, and local terrain. Across Delaware, last spring frost dates span about 9 days — from around March 29 near Lewes to April 7 near Newark Ag Farm. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.