September weather forecast
Richland, WA

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Weather in September

September brings a significant change in the climate of Richland as the autumn season kicks in. The temperatures begin to drop noticeably and the greenery starts turning rustic, indicating summer's end. The typically clear September skies are now interspersed with clouds. Though the city experiences a nominal amount of rainfall, around 0.2" (5mm). Sunny days followed by cool evenings are a common sight in September, signaling a transition toward the cooler months.

Temperature

The transition into September is accompanied by a temperature decrease, with the average high-temperature shifting from a hot 89.4°F (31.9°C) in August to a warm 78.6°F (25.9°C). In September, the average low-temperature in Richland records at a mild 57°F (13.9°C) during the nights.

Humidity

In September, the average relative humidity in Richland is 43%.

Rainfall

July and September are months with the least rain when the rain falls for 4 days and typically aggregates up to 0.2" (5mm) of rain.

Snowfall

April through October are months without snowfall.

Daylight

In Richland, the average length of the day in September is 12h and 32min.
On the first day of September, sunrise is at 6:18 am and sunset at 7:35 pm. On the last day of the month, sunrise is at 6:55 am and sunset at 6:38 pm PDT.

Sunshine

The average sunshine in September is 10.9h.

UV index

The average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a moderate health risk from exposure to the Sun's UV rays for the average person.
Note: The daily high UV index of 5 during September translates into the following recommendations:
Be vigilant - A duty to shield skin and eyes from injury exists. To avoid the Sun's strongest rays, limit exposure around the mid-day period. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Updated: Feb 14, 2024 | Published by: Weather Atlas | Resources

Frequently asked questions

What are September temperatures in Richland?

In September, the average high-temperature and low-temperature in Richland, Washington, are 78.6°F (25.9°C) and 57°F (13.9°C) respectively.

What is the average humidity in September in Richland?

In September, the average relative humidity is 43%.

What is the driest month in Richland?

The months with the least rainfall in Richland, Washington, are July and September Rain falls for 4 days and accumulates 0.2" (5mm) of rain.

How much does it rain in Richland in September?

In September, in Richland, the rain falls for 4 days. Throughout September, 0.2" (5mm) of precipitation is accumulated.

When it does not snow in Richland?

April through October are months without snowfall.

How many hours of daylight does Richland have in September?

In September, the average day length in Richland, Washington, is 12h and 32min.

When are sunrise and sunset in September in Richland?

On the first day of September in Richland, Washington, sunrise is at 6:18 am and sunset at 7:35 pm. On the last day of the month, sunrise is at 6:55 am and sunset at 6:38 pm PDT.

How many hours of sunshine does Richland have in September?

In Richland, Washington, the average sunshine duration in September is 10.9h.

What is the UV index intensity in September in Richland?

In September, the average daily maximum UV index in Richland, Washington, is 5. A UV Index reading of 3 to 5 represents a moderate health threat from unsafe exposure to Sun's UV rays.
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
Richland, WA

Average temperature in September - Richland, WA
  • Average high temperature in September: 78.6°F

The warmest month (with the highest average high temperature) is July (90.1°F).
The month with the lowest average high temperature is December (38.1°F).

  • Average low temperature in September: 57°F

The month with the highest average low temperature is August (64.2°F).
The coldest month (with the lowest average low temperature) is December (27.5°F).

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Average pressure in September
Richland, WA

Average pressure in September - Richland, WA
  • Average pressure in September: 29.95"Hg

The month with the highest atmospheric pressure is January (30.18"Hg).
The month with the lowest atmospheric pressure is August (29.91"Hg).

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Average wind speed in September
Richland, WA

Average wind speed in September - Richland, WA
  • Average wind speed in September: 6.6mph

The windiest month (with the highest average wind speed) is April (8.3mph).
The calmest month (with the lowest average wind speed) is December (5.6mph).

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Average humidity in September
Richland, WA

Average humidity in September - Richland, WA
  • Average humidity in September: 43%

The month with the highest relative humidity is January (81%).
The month with the lowest relative humidity is July (35%).

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Average rainfall in September
Richland, WA

Average rainfall in September - Richland, WA
  • Average rainfall in September: 0.2"

The wettest month (with the highest rainfall) is December (0.94").
The driest months (with the least rainfall) are July and September (0.2").

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Average rainfall days in September
Richland, WA

Average rainfall days in September - Richland, WA
  • Average rainfall days in September: 4 days

The month with the highest number of rainy days is March (12.3 days).
The month with the least rainy days is July (3.5 days).

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Average snowfall in September
Richland, WA

Average snowfall in September - Richland, WA
  • Average snowfall in September: 0"

The month with the highest snowfall is February (2.2").
The months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days in September
Richland, WA

Average snowfall days in September - Richland, WA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is December (3.3 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).

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Average daylight in September /
Average sunshine in September
Richland, WA

Average daylight in September / Average sunshine in September - Richland, 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: 10h and 5min

The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is January (Average sunshine: 5h and 24min).

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Average sunshine days in September
Richland, WA

Average sunshine days in September - Richland, WA
  • Average sunshine days in September: 24.2 days

The month with the most sunshine days is July (25.7 days).
The months with the least sunshine days are February and March (15.3 days).

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Average UV index in September
Richland, WA

Average UV index in September - Richland, WA
  • Average UV index in September: 5

The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in September
Richland, WA

Average cloud cover in September - Richland, WA
  • Average cloud cover in September: 16

The month with the most cloud cover is January (Cloud cover 44).
The month with the least cloud cover is July (Cloud cover 9).

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Average visibility in September
Richland, WA

Average visibility in September - Richland, WA
  • Average visibility in September: 6mi

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

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Richland, Washington, USA

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