Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
With September's arrival, Mountain Brook, Washington, sees a decrease in average high-temperatures, moving from a moderately hot 78.6°F (25.9°C) in August to a pleasant 69.1°F (20.6°C). During September, the nighttime temperature averages of 47.7°F (8.7°C).Humidity
In September, the average relative humidity is 65%.Rainfall
In Mountain Brook, during September, the rain falls for 8.2 days and regularly aggregates up to 0.91" (23mm) of precipitation. Throughout the year, there are 152.5 rainfall days, and 26.93" (684mm) of precipitation is accumulated.Snowfall
In Mountain Brook, snow does not fall in May through October.Daylight
The average length of the day in September in Mountain Brook is 12h and 31min.On the first day of the month, sunrise is at 6:27 am and sunset at 7:43 pm. On the last day of September, sunrise is at 7:03 am and sunset at 6:46 pm PDT.
Sunshine
In September, the average sunshine in Mountain Brook, Washington, is 10.2h.UV index
In September, the average daily maximum UV index in Mountain Brook is 3. A UV Index reading of 3 to 5 represents a medium health hazard from unsafe exposure to UV radiation for the average person.Note: In September, the average maximum UV index of 3 translates into the following recommendations:
Exercise care. People with light skin might get burns in fewer than 30 minutes. The midday Sun can be dangerous due to its intense radiation; always find shade and reduce exposure. A hat with a broad brim is indispensable, filtering out up to half of UV rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the temperature in September in Mountain Brook?
What is the average humidity in September in Mountain Brook?
How many days does it rain in September in Mountain Brook?
When it does not snow in Mountain Brook?
What is the average length of the day in September in Mountain Brook?
When is the sunrise / sunset in September in Mountain Brook?
How long on average sun shines in September in Mountain Brook?
What is the UV index reading in September in Mountain Brook?
Average temperature in September
Mountain Brook, WA
- Average high temperature in September: 69.1°F
The warmest month (with the highest average high temperature) is August (78.6°F).
The month with the lowest average high temperature is December (35.2°F).
- Average low temperature in September: 47.7°F
The month with the highest average low temperature is August (52.3°F).
The coldest month (with the lowest average low temperature) is December (26.1°F).
Average pressure in September
Mountain Brook, WA
- Average pressure in September: 29.99"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is August (29.97"Hg).
Average wind speed in September
Mountain Brook, WA
- Average wind speed in September: 5.2mph
The windiest month (with the highest average wind speed) is June (6.4mph).
The calmest month (with the lowest average wind speed) is October (4.8mph).
Average humidity in September
Mountain Brook, WA
- Average humidity in September: 65%
The months with the highest relative humidity are January, February and December (88%).
The months with the lowest relative humidity are July and August (58%).
Average rainfall in September
Mountain Brook, WA
- Average rainfall in September: 0.91"
The wettest month (with the highest rainfall) is January (4.88").
The driest month (with the least rainfall) is July (0.24").
Average rainfall days in September
Mountain Brook, WA
- Average rainfall days in September: 8.2 days
The month with the highest number of rainy days is March (19.4 days).
The month with the least rainy days is August (3.8 days).
Average snowfall in September
Mountain Brook, WA
- Average snowfall in September: 0"
The month with the highest snowfall is January (6.22").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Mountain Brook, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is December (6.5 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
Mountain Brook, 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 1min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is January (Average sunshine: 3h and 54min).
Average sunshine days in September
Mountain Brook, WA
- Average sunshine days in September: 20.4 days
The month with the most sunshine days is July (25.8 days).
The month with the least sunshine days is February (8.8 days).
Average UV index in September
Mountain Brook, WA
- Average UV index in September: 3
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January and February (UV index 1).
Average cloud cover in September
Mountain Brook, WA
- Average cloud cover in September: 27
The months with the most cloud cover are January and February (Cloud cover 61).
The months with the least cloud cover are July and August (Cloud cover 15).
Average visibility in September
Mountain Brook, WA
- Average visibility in September: 6mi
The months with the highest visibility are May, June, July, August and September (6mi).
The months with the lowest visibility are January, February and December (4mi).
Mountain Brook, Washington, USA
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