Delaware weather and outdoor projects
Delaware has a humid climate with hot summers and fairly mild winters for the Mid-Atlantic, moderated by Delaware Bay and the Atlantic. Rain is spread through the year, and summer brings humid days with afternoon storms.
Spring and early fall give the best combinations of mild temperatures and lower humidity for deck staining and exterior painting. Coastal areas in Sussex County see salt air and wind that are hard on finishes, so a good deck stain and regular maintenance pay off. Winter freezes are common but usually short, and concrete poured from December to February needs protection on cold nights.
Frost dates in Delaware
In Wilmington, the median last spring freeze (32°F) is around April 7 and the median first fall freeze is around November 1, a frost-free season of about 209 days.
Frost dates matter for concrete, which must not freeze in its first 48 hours, for paint and caulk that need nights above their minimum, and for lawn care, since crabgrass preventer goes down as the soil warms in spring. See how late in fall you can stain, paint or seal.
Best time to stain a deck in Delaware
In Wilmington, the most reliable months are May–September. April and October can also work on the right days. December–March is too cold, with average highs around 46°F. In November, nights average about 37°F, too cold for the coating to dry and cure overnight. In April and October, nights average about 45°F, so finish early on mild days and check the overnight low.
Check this week’s hour-by-hour verdict with the deck staining forecast.
Best time to paint outside in Delaware
In Wilmington, the most reliable months are May–October. March–April and November can also work on the right days. December–February is too cold, with average highs around 44°F. March and November are cool, with highs around 54°F, so choose the warmest afternoons. In April, nights average about 44°F, so finish early on mild days and check the overnight low.
Check this week’s hour-by-hour verdict with the exterior painting forecast.
Best time to pour concrete in Delaware
In Wilmington, the most reliable months are May–October. April can also work on the right days. November–March averages about 18 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. April brings about 2 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
Check this week’s hour-by-hour verdict with the concrete pouring forecast.
Best time to seal a driveway in Delaware
In Wilmington, the most reliable months are May–September. April and October can also work on the right days. November–March is too cold, with average highs around 48°F. April and October are cool, with highs around 66°F, so choose the warmest afternoons.
Check this week’s hour-by-hour verdict with the driveway sealing forecast.
Best time to fertilize or treat a lawn in Delaware
In Wilmington, the most reliable months are April–June and August–October. March, July and November can also work on the right days. December–February is too cold, with average highs around 44°F. March and November are cool, with highs around 54°F, so choose the warmest afternoons. July is hot, with highs near 87°F, so start early and keep out of full afternoon sun.
Check this week’s hour-by-hour verdict with the lawn fertilizer forecast.
Monthly weather in Wilmington
| Month | Avg high | Avg low | Wet days* | Rain | Freezing nights |
|---|---|---|---|---|---|
| January | 41°F | 26°F | 6 | 3.2 in | 24 |
| February | 44°F | 27°F | 6 | 2.8 in | 21 |
| March | 53°F | 34°F | 7 | 4.2 in | 14 |
| April | 64°F | 44°F | 7 | 3.5 in | 2 |
| May | 74°F | 53°F | 7 | 3.6 in | 0 |
| June | 82°F | 63°F | 7 | 4.7 in | 0 |
| July | 87°F | 68°F | 7 | 4.4 in | 0 |
| August | 85°F | 67°F | 6 | 4.0 in | 0 |
| September | 79°F | 59°F | 6 | 4.4 in | 0 |
| October | 67°F | 47°F | 6 | 3.7 in | 1 |
| November | 56°F | 37°F | 6 | 3.1 in | 10 |
| December | 46°F | 30°F | 7 | 3.9 in | 20 |
*Days with at least 0.1 inch of rain or melted snow. Freezing nights: average nights a month at or below 32°F. Humidity is calculated from NOAA hourly normal temperature and dew point at 3 PM.
Use the averages, then check the forecast
These ratings describe a typical month, not a particular week. A warm spell in a “poor” month can give you a good day, and a wet week can spoil a “good” one. Use this page to plan the season, then check the 7-day forecast for your ZIP code before you buy materials or book help. Each project forecast checks the hours after you finish too: overnight lows, dew and rain that would ruin fresh stain, paint, sealer or concrete.
About this data
Monthly temperatures, rain days, snowfall and freeze dates are NOAA National Centers for Environmental Information (NCEI) U.S. Climate Normals for 1991–2020 at WILMINGTON NEW CASTLE CO AP. Ratings apply the same temperature limits as our forecasts (for example, 50°F or warmer for deck stain and driveway sealer, and no freezing nights for new concrete) to the average month. Your product label always takes priority.
Frequently asked questions
When is the best time to stain a deck in Delaware?
In Wilmington, May–September. Look for at least 24 dry hours before and after, and nights above about 40°F. The deck staining forecast checks your exact week.
When is the last frost in Delaware?
Wilmington: around April 7. These are median dates from NOAA 1991–2020 normals, so a freeze after them happens in about half of years. Low spots and valleys freeze later in spring.
Can you pour concrete in winter in Delaware?
Yes, but it needs cold-weather practices. Wilmington averages about 65 freezing nights from December to February, so fresh concrete needs insulated blankets, a heated enclosure or an accelerated mix, and must not freeze in the first 48 hours. Many homeowners wait for spring.
What months are best for sealing a driveway in Delaware?
In Wilmington, May–September. Most sealers need 50°F or warmer for 24 hours and a dry day after. See the driveway sealing forecast.