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
September reveals a small adjustment in temperature, transitioning from an average high of a hot 89.2°F (31.8°C) in August to a moderately hot 83.8°F (28.8°C). September nights in Grass Valley see a notable contrast from daytime highs, with the nighttime temperature averaging at a refreshing 56.5°F (13.6°C).Heat index
In September, the heat index is estimated at 82.4°F (28°C). Constant activity during exposure could result in a state of weariness and possibly heat cramps.Consider that heat index readings are for situations in the shade and light wind. Heat index values may be hiked up by 15 Fahrenheit (8 Celsius) degrees under direct sunshine.
Note: The heat index, also known as 'apparent temperature' or 'feels like', marries air temperature and humidity to produce a value illustrating perceived warmth. The impact of weather is individual, with diverse individuals experiencing it differently due to variations in body mass, height, and activity levels. Consider the sun's direct rays and their impact; they can potentially increase the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical to babies and toddlers. Typically, children face more danger than adults as they usually perspire less. Their larger skin surface relative to their small bodies and increased heat output from their activities enhance their risk.
Humidity
In Grass Valley, California, the average relative humidity in September is 40%.Rainfall
In September, the rain falls for 2.3 days. Throughout September, 0.28" (7mm) of precipitation is accumulated. Throughout the year, in Grass Valley, there are 82 rainfall days, and 33.11" (841mm) of precipitation is accumulated.Snowfall
In Grass Valley, snow does not fall in June through October.Daylight
In Grass Valley, the average length of the day in September is 12h and 26min.On the first day of the month, sunrise is at 6:33 am and sunset at 7:34 pm. On the last day of September, sunrise is at 7:00 am and sunset at 6:47 pm PDT.
Sunshine
In Grass Valley, the average sunshine in September is 11.2h.UV index
The average daily maximum UV index in September in Grass Valley is 5. A UV Index of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for ordinary individuals.Note: The daily high UV index of 5 during September translates 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. For a sun-safe wardrobe, go for clothes that are tightly woven and generously sized.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How hot is September in Grass Valley?
What is the average humidity in September in Grass Valley?
How many days does it rain in September in Grass Valley?
When it does not snow in Grass Valley?
What is the average length of the day in September in Grass Valley?
When are sunrise and sunset in September in Grass Valley?
How many hours of sunshine does Grass Valley have in September?
How high is the UV index in September in Grass Valley?
Average temperature in September
Grass Valley, CA
- Average high temperature in September: 83.8°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 (51.3°F).
- Average low temperature in September: 56.5°F
The month with the highest average low temperature is July (60.1°F).
The coldest month (with the lowest average low temperature) is December (37.2°F).
Average pressure in September
Grass Valley, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.17"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).
Average wind speed in September
Grass Valley, CA
- Average wind speed in September: 5.2mph
The windiest month (with the highest average wind speed) is February (6mph).
The calmest month (with the lowest average wind speed) is August (4.8mph).
Average humidity in September
Grass Valley, CA
- Average humidity in September: 40%
The month with the highest relative humidity is March (75%).
The month with the lowest relative humidity is July (37%).
Average rainfall in September
Grass Valley, CA
- Average rainfall in September: 0.28"
The wettest month (with the highest rainfall) is March (6.57").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in September
Grass Valley, CA
- Average rainfall days in September: 2.3 days
The month with the highest number of rainy days is March (15.1 days).
The month with the least rainy days is July (1.1 days).
Average snowfall in September
Grass Valley, CA
- Average snowfall in September: 0"
The month with the highest snowfall is February (6.42").
The months with the least snowfall are June, July, August, September and October (0").
Average snowfall days in September
Grass Valley, CA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is March (2.4 days).
The months with the least snowfall days are June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Grass Valley, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in September: 11h and 1min
The month with the most sunshine is July (Average sunshine: 12h and 12min).
The month with the least sunshine is January (Average sunshine: 5h and 42min).
Average sunshine days in September
Grass Valley, CA
- Average sunshine days in September: 26.9 days
The month with the most sunshine days is July (29.8 days).
The month with the least sunshine days is March (14.8 days).
Average UV index in September
Grass Valley, CA
- Average UV index in September: 5
The month with the highest UV index is July (UV index 7).
The month with the lowest UV index is November (UV index 2).
Average cloud cover in September
Grass Valley, CA
- Average cloud cover in September: 8
The month with the most cloud cover is March (Cloud cover 41).
The month with the least cloud cover is July (Cloud cover 4).
Average visibility in September
Grass Valley, CA
- 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).
Grass Valley, California, USA
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