September weather forecast and climate
New Castle, DE

Weather in September

The first month of the autumn, September, is still a warm month in New Castle, Delaware, with average temperature varying between 60.6°F (15.9°C) and 76.3°F (24.6°C).

Temperature

In September, the average high-temperature slightly decreases, from 82.9°F (28.3°C) in August, to a still warm 76.3°F (24.6°C). In New Castle, in September, the average low-temperature is 60.6°F (15.9°C).

Humidity

The average relative humidity in September is 77%.

Rainfall

In New Castle, during 11.2 rainfall days, 1.42" (36mm) of precipitation is typically accumulated. In New Castle, during the entire year, the rain falls for 143.2 days and collects up to 21.89" (556mm) of precipitation.

Snowfall

May through October are months without snowfall.

Ocean temperature

In New Castle, Delaware, in September, the average water temperature is 72.1°F (22.3°C).
Note: Depending on a person's sensitivity to cold, with regards to sunshine, wind, and air temperature, a quick swim in 72.1°F (22.3°C) water may be enjoyable. (FYI: The official water temperature required for the Olympic swimming competition is 77°F (25°C) to 82.4°F (28°C).)

Daylight

The average length of the day is 12.4h.

Sunshine

The average sunshine is 9.2h.

UV index

In New Castle, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a moderate threat to health from unsafe exposure to the UV radiation for the ordinary person.
Note: In September, the average maximum UV index of 5 translate into the following recommendations:
Take precautions - Protection against sunburn is recommended. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Beware! The reflection of water and sand dramatically increases exposure to the UV rays.
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FAQ

What is the temperature in September in New Castle?

In New Castle, in September, the average high-temperature is 76.3°F (24.6°C), and the average low-temperature is 60.6°F (15.9°C).

What is the average humidity in September in New Castle?

In New Castle, the average relative humidity in September is 77%.

How many days does it rain in September in New Castle?

In September, the rain falls for 11.2 days. Throughout September, 1.42" (36mm) of precipitation is accumulated.

When it does not snow in New Castle?

May through October are months without snowfall.

What is the ocean temperature in September in New Castle?

In New Castle, in September, the average water temperature is 72.1°F (22.3°C). A person's cold intolerance, with sunshine, wind, and air temperature, are essential factors for enjoying swimming in 72.1°F (22.3°C) water.

How many hours of daylight does New Castle have in September?

The average length of the day in September in New Castle, Delaware, is 12.4h.

How many hours of sunshine does New Castle have in September?

The average sunshine in September is 9.2h.

What is the UV index intensity in September in New Castle?

In New Castle, the average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a moderate health threat from the exposure to the Sun's UV radiation.

Average temperature in September
New Castle, DE

Average temperature in September - New Castle, DE
  • Average high temperature in September: 76.3°F

The warmest month (with the highest average high temperature) is July (84.9°F).
The month with the lowest average high temperature is January (37.8°F).

  • Average low temperature in September: 60.6°F

The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (26.1°F).

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Average pressure in September
New Castle, DE

Average pressure in September - New Castle, DE
  • Average pressure in September: 30.05"

The month with the highest atmospheric pressure is November (30.13").
The month with the lowest atmospheric pressure is June (29.94").

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Average wind speed in September
New Castle, DE

Average wind speed in September - New Castle, DE
  • Average wind speed in September: 6mph

The windiest months (with the highest average wind speed) are February and March (8.8mph).
The calmest month (with the lowest average wind speed) is August (5.4mph).

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Average humidity in September
New Castle, DE

Average humidity in September - New Castle, DE
  • Average humidity in September: 77%

The month with the highest relative humidity is October (78%).
The month with the lowest relative humidity is April (72%).

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Average rainfall in September
New Castle, DE

Average rainfall in September - New Castle, DE
  • Average rainfall in September: 1.42"

The wettest month (with the highest rainfall) is August (2.83").
The driest month (with the least rainfall) is January (1.38").

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Average rainfall days in September
New Castle, DE

Average rainfall days in September - New Castle, DE
  • Average rainfall days in September: 11.2 days

The month with the highest number of rainy days is May (16.8 days).
The month with the least rainy days is January (7.8 days).

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Average snowfall in September
New Castle, DE

Average snowfall in September - New Castle, DE
  • Average snowfall in September: 0"

The month with the highest snowfall is January (1.69").
Months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in September
New Castle, DE

Average snowfall days in September - New Castle, DE
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (5.2 days).
Months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average sea temperature in September
New Castle, DE

Average sea temperature in September - New Castle, DE
  • Average sea temperature in September: 72.1°F

The best month for swimming (with the highest average sea temperature) is August (76.3°F).
The coldest month (with the lowest average sea temperature) is February (40.9°F).

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Average daylight in September /
Average sunshine in September
New Castle, DE

Average daylight in September / Average sunshine in September - New Castle, DE
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 14.9h).
The month with the shortest days is December (Average daylight: 9.4h).

  • Average sunshine in September: 9.2h

The month with the most sunshine is July (Average sunshine: 10.8h).
The month with the least sunshine is February (Average sunshine: 4.9h).

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Average sunshine days in September
New Castle, DE

Average sunshine days in September - New Castle, DE
  • Average sunshine days in September: 17.6 days

The month with the most sunshine days is November (20.1 days).
The month with the least sunshine days is May (11.8 days).

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Average UV index in September
New Castle, DE

Average UV index in September - New Castle, DE
  • Average UV index in September: 5

Months with the highest UV index are May, June, July and August (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in September
New Castle, DE

Average cloud cover in September - New Castle, DE
  • Average cloud cover in September: 35

Months with the most cloud cover are February and March (Cloud cover 46).
The month with the least cloud cover is July (Cloud cover 30).

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Average visibility in September
New Castle, DE

Average visibility in September - New Castle, DE
  • Average visibility in September: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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