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
In Riley, the month of December registers the lowest temperatures, averaging 33.1°F (0.6°C) at the peak and 21.2°F (-6°C) at the lowest.Humidity
December is the most humid month in Riley, with an average relative humidity of 83%.Rainfall
The month with the most rainfall in Riley is December, when the rain falls for 13.6 days and typically aggregates up to 1.54" (39mm) of precipitation.Snowfall
January through March, November and December are months with snowfall. The month with the most snowfall in Riley is December, when snow falls for 3.1 days and typically aggregates up to 0.87" (22mm) of snow.Daylight
With an average of 9h and 0min of daylight, December has the shortest days of the year.On the first day of the month, sunrise is at 7:12 am and sunset at 4:22 pm. On the last day of December, in Riley, sunrise is at 7:31 am and sunset at 4:31 pm PST.
Sunshine
The month with the least sunshine is December, with an average of 5.2h of sunshine.UV index
The months with the lowest UV index are January through March, November and December, with an average maximum UV index of 2. A UV Index estimate of 2, and below, represents a minimal health vulnerability from unsafe exposure to UV radiation for average individuals.Note: A typical high UV index of 2 in December suggests the following recommendations:
Most individuals face no significant issues with extended sun exposure, but it is always essential to protect children, babies, and those with sensitive skin. Stay safe from the Sun's strongest UV rays by limiting exposure during midday. Clothes that are both tight-knit and comfortably loose are prime choices for sun protection. Note this! The Sun's UV radiation can nearly be doubled by the reflection off snow.
Frequently asked questions
What is the coldest month in Riley?
How cold is December in Riley?
What is the most humid month in Riley?
What is the average humidity in December in Riley?
What is the wettest month in Riley?
How much does it rain in Riley in December?
What is the snowiest month in Riley?
How many days does it snow in December in Riley?
What is the month with the shortest days in Riley?
What is the average length of the day in December in Riley?
When is the sunrise / sunset in December in Riley?
What is the month with the least sunshine in Riley?
How long on average sun shines in December in Riley?
What is the month with the lowest UV index in Riley?
What is the UV index reading in December in Riley?
Average temperature in December
Riley, OR
- Average high temperature in December: 33.1°F
The warmest month (with the highest average high temperature) is July (82.9°F).
The month with the lowest average high temperature is December (33.1°F).
- Average low temperature in December: 21.2°F
The month with the highest average low temperature is August (58.1°F).
The coldest month (with the lowest average low temperature) is December (21.2°F).
Average pressure in December
Riley, OR
- Average pressure in December: 30.19"Hg
The month with the highest atmospheric pressure is January (30.22"Hg).
The month with the lowest atmospheric pressure is August (29.94"Hg).
Average wind speed in December
Riley, OR
- Average wind speed in December: 7.9mph
The windiest month (with the highest average wind speed) is April (9.9mph).
The calmest month (with the lowest average wind speed) is August (7.5mph).
Average humidity in December
Riley, OR
- Average humidity in December: 83%
The month with the highest relative humidity is December (83%).
The months with the lowest relative humidity are July and August (33%).
Average rainfall in December
Riley, OR
- Average rainfall in December: 1.54"
The wettest month (with the highest rainfall) is December (1.54").
The driest month (with the least rainfall) is July (0.16").
Average rainfall days in December
Riley, OR
- Average rainfall days in December: 13.6 days
The month with the highest number of rainy days is March (17.7 days).
The month with the least rainy days is August (3.3 days).
Average snowfall in December
Riley, OR
- Average snowfall in December: 0.87"
The month with the highest snowfall is December (0.87").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in December
Riley, OR
- Average snowfall days in December: 3.1 days
The month with the highest number of snowfall days is December (3.1 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).
Average daylight in December /
Average sunshine in December
Riley, OR
- Average daylight in December: 9h and 0min
The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).
- Average sunshine in December: 5h and 1min
The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 5h and 12min).
Average sunshine days in December
Riley, OR
- Average sunshine days in December: 14.5 days
The months with the most sunshine days are July and August (25.3 days).
The month with the least sunshine days is March (11.5 days).
Average UV index in December
Riley, OR
- Average UV index in December: 2
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in December
Riley, OR
- Average cloud cover in December: 47
The month with the most cloud cover is December (Cloud cover 47).
The months with the least cloud cover are July and August (Cloud cover 9).
Average visibility in December
Riley, OR
- Average visibility in December: 6mi
The months with the highest visibility are February, March, April, May, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is January (5mi).
Riley, Oregon, USA
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