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United States weather

Weather in New Castle County, Delaware for September 2025

Your guide to New Castle County weather in September - trends and predictions

    Temperatures

  • Until now, September 2025 in New Castle County is slightly cooler than the historical average by -1.6 °F.

  • The forecast for the next days in New Castle County predicts temperatures to be around 25 °F, close to the historical average.

  • In general, the average temperature in New Castle County at the beginning of September is 28.3 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 25.1 °F by the end of September.

    • Rain 🌧️

  • New Castle County in September brings notable rainfall, with an average of 17 rainy days and a total precipitation of 223.9 mm.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
13
Dry days
Average rainy days
17
Rainy days
Average snowy days
0
Snow days
Average temperatures
25°/15°
Temperatures
Average wind speed
15 km/h
Avg max wind
Average humidity
74 %
Avg humidity

New Castle County Weather September

Move between months or click on a day
August
October
Sun.Mon.Tue.Wed.Thu.Fri.Sat.
1
Sunny
27°
2
Sunny
27°
3
Partly cloudy
26°
4
Thundery outbreaks possible
30°
5
Cloudy
31°
6
Sunny
31°
7
Thundery outbreaks possible
26°
8
Sunny
27°
9
Thundery outbreaks possible
26°
10
Moderate or heavy rain shower
26°
11
Light rain shower
27°
12
Moderate rain at times
28°
13
Torrential rain shower
26°
14
Sunny
28°
15
Sunny
27°
16
Overcast
25°
17
Moderate rain
22°
18
Partly cloudy
30°
19
Sunny
32°
20
Cloudy
20°
21
Patchy rain possible
21°
22
Cloudy
26°
23
Patchy rain possible
28°
24
Patchy rain possible
28°
25
Overcast
23°
26
Patchy rain possible
22°
27
Patchy rain possible
24°
28
Patchy rain possible
31°
29
Patchy rain possible
31°
30
Patchy rain possible
17°

Temperatures trend during September in New Castle County

See the weather trend as well as the moving average line

September weather in New Castle County day by day

Click on a date for more information
August October
Date Weather Temperatures Rain UV More
Sept. 1 Sunny
Sunny
 27° /16° 1.5 mm 6
Sept. 2 Sunny
Sunny
 27° /15° 0 mm 6
Sept. 3 Partly cloudy
Partly cloudy
 26° /14° 0 mm 6
Sept. 4 Thundery outbreaks possible
Thundery outbreaks possible
 30° /16° 0 mm 6
Sept. 5 Cloudy
Cloudy
 31° /18° 6.1 mm 7
Sept. 6 Sunny
Sunny
 31° /20° 7.4 mm 7
Sept. 7 Thundery outbreaks possible
Thundery outbreaks possible
 26° /16° 25.9 mm 6
Sept. 8 Sunny
Sunny
 27° /13° 2.2 mm 7
Sept. 9 Thundery outbreaks possible
Thundery outbreaks possible
 26° /14° 5.4 mm 6
Sept. 10 Moderate or heavy rain shower
Moderate or heavy rain shower
 26° /16° 4.7 mm 6
Sept. 11 Light rain shower
Light rain shower
 27° /16° 1.9 mm 7
Sept. 12 Moderate rain at times
Moderate rain at times
 28° /16° 1.2 mm 7
Sept. 13 Torrential rain shower
Torrential rain shower
 26° /16° 7.9 mm 6
Sept. 14 Sunny
Sunny
 28° /16° 0 mm 7
Sept. 15 Sunny
Sunny
 27° /14° 0 mm 7
Sept. 16 Overcast
Overcast
 25° /13° 0 mm 6
Sept. 17 Moderate rain
Moderate rain
 22° /15° 4 mm 5
Sept. 18 Partly cloudy
Partly cloudy
 30° /17° 0 mm 1.2
Sept. 19 Sunny
Sunny
 32° /16° 0 mm 1.4
Sept. 20 Cloudy
Cloudy
 20° /17° 0 mm 1.4
Sept. 21 Patchy rain possible
Patchy rain possible
 21° /17° 4.5 mm 0.4
Sept. 22 Cloudy
Cloudy
 26° /14° 0 mm 0
Sept. 23 Patchy rain possible
Patchy rain possible
 28° /17° 0.2 mm 5
Sept. 24 Patchy rain possible
Patchy rain possible
 28° /20° 0.8 mm 5
Sept. 25 Overcast
Overcast
 23° /19° 0.1 mm 5
Sept. 26 Patchy rain possible
Patchy rain possible
 22° /18° 0 mm 4
Sept. 27 Patchy rain possible
Patchy rain possible
 24° /18° 0.1 mm 5
Sept. 28 Patchy rain possible
Patchy rain possible
 31° /19° 0.2 mm 5
Sept. 29 Patchy rain possible
Patchy rain possible
 31° /20° 0.9 mm 5
Sept. 30 Patchy rain possible
Patchy rain possible
 17° /16° 3.9 mm 4
Next
Important Notice
Our weather forecast for New Castle County in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the New Castle County forecast closer to your planned date for the most up-to-date weather information.
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New Castle County in September - FAQ

What are the expected maximum and minimum temperatures in New Castle County during September?
During September, expect a variety of temperatures with highs around 25° and lows near 15°, suitable for diverse activities and preferences.
How much rainfall should be expected in New Castle County during September?
Significant rainfall exceeding 223.9 mm is expected in New Castle County during September, occurring over more than 17 days. Preparing for wet conditions is recommended in your planning.
What are the typical wind conditions in New Castle County during September?
The average wind speed in New Castle County during September is 15 km/h, suggesting breezy to windy conditions, depending on your activities.

September rainfall patterns in New Castle County

Explore the daily rainfall trends and prepare for New Castle Countys September weather 💧

UV exposure in New Castle County during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Location coordinates Where is New Castle County?

Get accurate weather forecasts for New Castle County, located at latitude 39.684 and longitude -75.75. Stay updated with localized weather information tailored for New Castle County.

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