September weather forecast
Castle Rock, WA

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Weather in September

September, the first month of the autumn in Castle Rock, is also an agreeable month, with an average temperature fluctuating between 70.7°F (21.5°C) and 47.1°F (8.4°C).

Temperature

September's arrival aligns with a minor decrease in average high-temperatures, from August's warm 77.7°F (25.4°C) to a pleasant 70.7°F (21.5°C). In the month of September, Castle Rock witnesses a marked temperature drop at night, averaging a low of 47.1°F (8.4°C).

Humidity

The average relative humidity in September in Castle Rock is 78%.

Rainfall

In Castle Rock, in September, during 10.3 rainfall days, 0.94" (24mm) of precipitation is typically accumulated. In Castle Rock, during the entire year, the rain falls for 157.3 days and collects up to 16.54" (420mm) of precipitation.

Snowfall

In Castle Rock, snow does not fall in April through October.

Daylight

The average length of the day in September in Castle Rock is 12h and 31min.
On the first day of the month, sunrise is at 6:33 am and sunset at 7:49 pm. On the last day of September, in Castle Rock, sunrise is at 7:09 am and sunset at 6:52 pm PDT.

Sunshine

In Castle Rock, the average sunshine in September is 8.5h.

UV index

In Castle Rock, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a medium health hazard from exposure to the Sun's UV rays for the average person.
Note: The maximum daily UV index of 4 in September converts into the following recommendations:
Preventative actions are necessary - The mandate to avoid skin and eye damage is in place. Avoiding direct sun during mid-day hours can prevent harmful UV radiation exposure. Combat UV radiation's detrimental effects with sun-safe clothing and UV-blocking eyewear.
Updated: Feb 14, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What is the usual temperature for Castle Rock in September?

An average high-temperature, in September, in Castle Rock, is 70.7°F (21.5°C) and the average low-temperature is 47.1°F (8.4°C).

What is the average humidity in September in Castle Rock?

In September, the average relative humidity in Castle Rock is 78%.

How much does it rain in Castle Rock in September?

In Castle Rock, during September, the rain falls for 10.3 days and regularly aggregates up to 0.94" (24mm) of precipitation.

When it does not snow in Castle Rock?

April through October are months without snowfall in Castle Rock.

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

In Castle Rock, the average day length in September is 12h and 31min.

When are sunrise and sunset in September in Castle Rock?

In September, on the first day of the month, sunrise is at 6:33 am and sunset at 7:49 pm. On the last day of the month, in Castle Rock, Washington, sunrise is at 7:09 am and sunset at 6:52 pm PDT.

How long on average sun shines in September in Castle Rock?

The average sunshine duration in September in Castle Rock is 8.5h.

What is the UV index reading in September in Castle Rock?

The average daily maximum UV index in September in Castle Rock is 4. A UV Index estimate of 3 to 5 represents a medium health risk from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Castle Rock, WA

Average temperature in September - Castle Rock, WA
  • Average high temperature in September: 70.7°F

The warmest month (with the highest average high temperature) is August (77.7°F).
The month with the lowest average high temperature is December (42.4°F).

  • Average low temperature in September: 47.1°F

The month with the highest average low temperature is August (49.6°F).
The coldest month (with the lowest average low temperature) is December (32.5°F).

Average pressure in September
Castle Rock, WA

Average pressure in September - Castle Rock, WA
  • Average pressure in September: 30.01"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are August and September (30.01"Hg).

Average wind speed in September
Castle Rock, WA

Average wind speed in September - Castle Rock, WA
  • Average wind speed in September: 3.7mph

The windiest month (with the highest average wind speed) is January (4.8mph).
The calmest months (with the lowest average wind speed) are August and September (3.7mph).

Average humidity in September
Castle Rock, WA

Average humidity in September - Castle Rock, WA
  • Average humidity in September: 78%

The months with the highest relative humidity are February and November (89%).
The months with the lowest relative humidity are July and August (73%).

Average rainfall in September
Castle Rock, WA

Average rainfall in September - Castle Rock, WA
  • Average rainfall in September: 0.94"

The wettest month (with the highest rainfall) is January (2.28").
The driest month (with the least rainfall) is August (0.31").

Average rainfall days in September
Castle Rock, WA

Average rainfall days in September - Castle Rock, WA
  • Average rainfall days in September: 10.3 days

The month with the highest number of rainy days is March (17.5 days).
The month with the least rainy days is July (6.1 days).

Average snowfall in September
Castle Rock, WA

Average snowfall in September - Castle Rock, WA
  • Average snowfall in September: 0"

The month with the highest snowfall is February (1.02").
The months with the least snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in September
Castle Rock, WA

Average snowfall days in September - Castle Rock, WA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (2.4 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

Average daylight in September /
Average sunshine in September
Castle Rock, WA

Average daylight in September / Average sunshine in September - Castle Rock, WA
  • Average daylight in September: 12h and 3min

The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).

  • Average sunshine in September: 8h and 3min

The month with the most sunshine is August (Average sunshine: 10h and 18min).
The month with the least sunshine is February (Average sunshine: 3h and 30min).

Average sunshine days in September
Castle Rock, WA

Average sunshine days in September - Castle Rock, WA
  • Average sunshine days in September: 17.5 days

The month with the most sunshine days is August (21.9 days).
The month with the least sunshine days is April (10.5 days).

Average UV index in September
Castle Rock, WA

Average UV index in September - Castle Rock, WA
  • Average UV index in September: 4

The months with the highest UV index are June and July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 2).

Average cloud cover in September
Castle Rock, WA

Average cloud cover in September - Castle Rock, WA
  • Average cloud cover in September: 45

The month with the most cloud cover is February (Cloud cover 65).
The month with the least cloud cover is August (Cloud cover 37).

Average visibility in September
Castle Rock, WA

Average visibility in September - Castle Rock, WA
  • Average visibility in September: 4mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (4mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (4mi).

Castle Rock, Washington, USA

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