New Castle, Delaware Weather
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Climate of New Castle: monthly averages
Based on 25 years of satellite and reanalysis data (2001-2025), July is usually the hottest month in New Castle, with average daytime highs around 30°C. January is the coolest, when nights typically fall to about -4°C and frost is possible on the coldest nights. That is a wide yearly range of roughly 34°C, so the seasons feel very different from each other.
The area receives about 1180 mm of rain in a typical year. Most of it falls from June to October and December (around 57% of the yearly total), and June is the wettest month at roughly 119 mm.
For outdoor plans and travel, May usually offers the most comfortable weather in New Castle, with mild days and relatively little rain.
| Month | Avg high | Avg low | Rainfall | Humidity |
|---|---|---|---|---|
| Jan | 4° | -4° | 73 mm | 84% |
| Feb | 5° | -3° | 74 mm | 82% |
| Mar | 10° | 0° | 92 mm | 80% |
| Apr | 17° | 6° | 93 mm | 78% |
| May | 22° | 12° | 95 mm | 79% |
| Jun | 27° | 17° | 119 mm | 76% |
| Jul | 30° | 21° | 118 mm | 72% |
| Aug | 30° | 20° | 116 mm | 73% |
| Sep | 26° | 16° | 104 mm | 74% |
| Oct | 19° | 9° | 109 mm | 78% |
| Nov | 13° | 3° | 86 mm | 81% |
| Dec | 7° | -1° | 103 mm | 85% |
Source: NASA POWER (MERRA-2 reanalysis), averaged over the roughly 50 km grid area around New Castle. Values describe typical conditions, not a forecast.
About New Castle weather
New Castle is set in Delaware's humid subtropical-to-continental climate on the mid-Atlantic coast, about 9 km south of Wilmington. Summers bring warm, humid summers (June–August). The year winds down with mild-to-cool winters (December–February) with occasional snow. This page shows live, auto-refreshing weather for New Castle: current conditions, an hourly breakdown, a 16-day outlook, a date-lookup tool for any past or future date, and real-time air quality, sourced from Open-Meteo. Local timezone: America/New_York.
Frequently asked questions
New Castle is about 9 km south of Wilmington, in Delaware.
New Castle sees mild-to-cool winters (December–February) with occasional snow.
The live current conditions, hourly forecast and 16-day outlook above are pulled in real time for New Castle's exact coordinates. No fixed schedule, the page updates whenever you load it.
July is usually the hottest month in New Castle, with average daytime highs of about 30°C and nights around 21°C.
The coldest nights come in January, when the average low is about -4°C and daytime highs reach around 4°C. Frost is possible on clear, calm nights.
New Castle receives about 1180 mm of rain in a typical year. June is the wettest month at roughly 119 mm, and the main rainy period is June to October and December.
May usually offers the most comfortable weather in New Castle, with mild daytime temperatures and little rain.
In November New Castle typically sees daytime highs near 13°C and lows near 3°C, with about 86 mm of rain over the month and average humidity around 81%. Check the live forecast above for this week's actual conditions.
Up to 16 days ahead using the extended forecast and date picker above; further-out or historical dates use the same date lookup tool.
Live temperature for New Castle is shown at the top of this page and refreshes automatically — see the hourly breakdown below for how it changes through the day.
New Castle's day-to-day weather follows the broader pattern of Delaware described above. See the hourly weather forecast or the air quality index for more detail.