September weather forecastLewiston, CA
September
Weather in September
The first month of the autumn, September, is still a warm month in Lewiston, California, with an average temperature varying between 46.2°F (7.9°C) and 77.9°F (25.5°C).Temperature
The transition to September results in a modest reduction in average high-temperature, moving from 84.6°F (29.2°C) in August to a still warm 77.9°F (25.5°C). Despite high daytime temperatures, the average temperature lowers to a frosty 46.2°F (7.9°C) during September nights.Humidity
In September, the average relative humidity is 57%.Rainfall
In Lewiston, in September, it is raining for 3.6 days, with typically 0.47" (12mm) of accumulated precipitation. Throughout the year, there are 119.2 rainfall days, and 33.35" (847mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Daylight
In Lewiston, the average length of the day in September is 12h and 27min.On the first day of September, sunrise is at 6:39 am and sunset at 7:42 pm. On the last day of the month, sunrise is at 7:07 am and sunset at 6:54 pm PDT.
Sunshine
In September, the average sunshine in Lewiston is 10.7h.UV index
The average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The maximum UV index, 4 during September, leads to the following recommendations:
Exercise prevention - Protecting skin and eyes from harm is required. Given the potency of the midday Sun's UV radiation, one should avoid prolonged exposure. Employ a hat with a wide brim for robust protection, cutting UV exposure by half.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Lewiston, CA
- Average high temperature in September: 77.9°F
The warmest months (with the highest average high temperature) are July and August (84.6°F).
The month with the lowest average high temperature is December (45°F).
- Average low temperature in September: 46.2°F
The month with the highest average low temperature is July (51.3°F).
The coldest month (with the lowest average low temperature) is December (30°F).
Average pressure in September
Lewiston, CA
- Average pressure in September: 29.95"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is August (29.94"Hg).
Average wind speed in September
Lewiston, CA
- Average wind speed in September: 3.7mph
The windiest months (with the highest average wind speed) are March and April (4.8mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).
Average humidity in September
Lewiston, CA
- Average humidity in September: 57%
The month with the highest relative humidity is March (82%).
The month with the lowest relative humidity is August (54%).
Average rainfall in September
Lewiston, CA
- Average rainfall in September: 0.47"
The wettest month (with the highest rainfall) is December (6.14").
The driest months (with the least rainfall) are July and August (0.16").
Average rainfall days in September
Lewiston, CA
- Average rainfall days in September: 3.6 days
The month with the highest number of rainy days is March (18.3 days).
The month with the least rainy days is August (2.5 days).
Average snowfall in September
Lewiston, CA
- Average snowfall in September: 0"
The month with the highest snowfall is February (8.35").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Lewiston, CA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (5.3 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
Lewiston, CA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 10h and 42min
The month with the most sunshine is July (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 4h and 36min).
Average sunshine days in September
Lewiston, CA
- Average sunshine days in September: 24.8 days
The month with the most sunshine days is August (26.8 days).
The month with the least sunshine days is March (10.6 days).
Average UV index in September
Lewiston, CA
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Lewiston, CA
- Average cloud cover in September: 16
The month with the most cloud cover is March (Cloud cover 54).
The month with the least cloud cover is August (Cloud cover 8).
Average visibility in September
Lewiston, CA
- Average visibility in September: 6mi
The months with the highest visibility are June, July, August, September and October (6mi).
The months with the lowest visibility are March and December (4mi).
