Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
Temperature readings reach their annual highs in December, averaging 32.4°F (0.2°C) and a minimum average of 20.7°F (-6.3°C).Humidity
The average relative humidity in December is 87%.Rainfall
The wettest months are January and December, with an average 1.57" (40mm) of rainfall.Snowfall
Months with snowfall are January through April, September, November and December. The month with the most snowfall is December, when snow falls for 9.5 days and typically aggregates up to 5.98" (152mm) of snow.Daylight
December has the shortest days of the year, with an average of 8h and 30min of daylight.On the first day of December, sunrise is at 7:27 am and sunset at 4:11 pm. On the last day of the month, sunrise is at 7:47 am and sunset at 4:20 pm PST.
Sunshine
The average sunshine in December is 4.9h.UV index
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2. A UV Index value of 2, and less, symbolizes a low threat to health from exposure to the Sun's UV rays for ordinary individuals.Note: The daily high UV index of 2 in December translates into this advice:
While most individuals can withstand prolonged sun exposure, it is imperative that babies, children, and those with sensitive skin always be shielded. Midday Sun has the strongest UV rays, making it crucial to limit exposure and find shade. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.
Frequently asked questions
What part of the year is the coldest in Rock Island?
How cold is it in Rock Island in December?
What is the average humidity in December in Rock Island?
What is the wettest month in Rock Island?
How many days does it rain in December in Rock Island?
What is the snowiest month in Rock Island?
How much does it snow in Rock Island in December?
What is the month with the shortest days in Rock Island?
What is the average length of the day in December in Rock Island?
What time are sunrise and sunset in December in Rock Island?
How long on average sun shines in December in Rock Island?
When is the lowest UV index in Rock Island?
What is the UV index intensity in December in Rock Island?
Average temperature in December
Rock Island, WA
- Average high temperature in December: 32.4°F
The warmest month (with the highest average high temperature) is July (83.1°F).
The month with the lowest average high temperature is December (32.4°F).
- Average low temperature in December: 20.7°F
The month with the highest average low temperature is August (56.3°F).
The coldest month (with the lowest average low temperature) is December (20.7°F).
Average pressure in December
Rock Island, WA
- Average pressure in December: 30.14"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is August (29.93"Hg).
Average wind speed in December
Rock Island, WA
- Average wind speed in December: 3.7mph
The windiest month (with the highest average wind speed) is June (6.5mph).
The calmest month (with the lowest average wind speed) is December (3.7mph).
Average humidity in December
Rock Island, WA
- Average humidity in December: 87%
The month with the highest relative humidity is January (88%).
The months with the lowest relative humidity are July and August (44%).
Average rainfall in December
Rock Island, WA
- Average rainfall in December: 1.57"
The wettest months (with the highest rainfall) are January and December (1.57").
The driest months (with the least rainfall) are July and August (0.24").
Average rainfall days in December
Rock Island, WA
- Average rainfall days in December: 9.7 days
The month with the highest number of rainy days is March (13.8 days).
The month with the least rainy days is August (3.8 days).
Average snowfall in December
Rock Island, WA
- Average snowfall in December: 5.98"
The month with the highest snowfall is December (5.98").
The months with the least snowfall are May, June, July, August and October (0").
Average snowfall days in December
Rock Island, WA
- Average snowfall days in December: 9.5 days
The month with the highest number of snowfall days is December (9.5 days).
The months with the least snowfall days are May, June, July, August and October (0 days).
Average daylight in December /
Average sunshine in December
Rock Island, WA
- Average daylight in December: 8h and 3min
The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).
- Average sunshine in December: 4h and 5min
The month with the most sunshine is August (Average sunshine: 12h and 6min).
The month with the least sunshine is January (Average sunshine: 4h and 42min).
Average sunshine days in December
Rock Island, WA
- Average sunshine days in December: 15.7 days
The month with the most sunshine days is July (25.5 days).
The month with the least sunshine days is February (12.6 days).
Average UV index in December
Rock Island, WA
- Average UV index in December: 2
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 December
Rock Island, WA
- Average cloud cover in December: 47
The month with the most cloud cover is January (Cloud cover 49).
The months with the least cloud cover are July and August (Cloud cover 11).
Average visibility in December
Rock Island, WA
- Average visibility in December: 4mi
The months with the highest visibility are March, April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January and December (4mi).
Rock Island, Washington, USA
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