December weather forecast
Roy, WA

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Weather in December

The first month of the winter, December, is still a chilly month in Roy, Washington, with an average temperature fluctuating between 43.5°F (6.4°C) and 34.2°F (1.2°C).

Temperature

December stands out as Roy's coldest month, with temperatures ranging between an average high of 43.5°F (6.4°C) and a low of 34.2°F (1.2°C).

Humidity

In Roy, the average relative humidity in December is 87%.

Rainfall

The month with the most rainfall in Roy is December, when the rain falls for 18.6 days and typically aggregates up to 4.96" (126mm) of precipitation.

Snowfall

January through April, November and December are months with snowfall. In Roy, during December, snow falls for 1.4 days and regularly aggregates up to 0.24" (6mm) of snow. In Roy, during the entire year, snow falls for 7.9 days and aggregates up to 4.45" (113mm) of snow.

Daylight

With an average of 8h and 36min of daylight, December has the shortest days of the year in Roy.
On the first day of the month, sunrise is at 7:36 am and sunset at 4:22 pm. On the last day of December, in Roy, Washington, sunrise is at 7:55 am and sunset at 4:31 pm PST.

Sunshine

With an average of 3.9h of sunshine, December has the least sunshine of the year in Roy.

UV index

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Roy, Washington. A UV Index estimate of 2, and below, represents a minimal health hazard from unsafe exposure to UV radiation for the average person.
Note: In December, a daily maximum UV index of 2 leads to the following instructions:
Most individuals face no major issues with lengthy exposure to the sun, but children, infants, and individuals with fair skin always require protection. Direct Sun exposure should be minimized especially during midday when radiation is most intense. Shield yourself from the harmful effects of UV radiation with sun-protective attire, a hat, and quality sunglasses. Forewarned is forearmed! The Sun's UV radiation can be almost doubled in intensity by snow reflection.
Updated: Feb 14, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What time of the year is the coldest in Roy?

Roy notes the coldest temperatures in December, with a average high of 43.5°F (6.4°C) and a low of 34.2°F (1.2°C).

How cold is December in Roy?

During December, Roy experiences an average high-temperature of 43.5°F (6.4°C) and a low-temperature of 34.2°F (1.2°C).

What is the average humidity in December in Roy?

The average relative humidity in December in Roy is 87%.

What is the wettest month in Roy?

December is the month with the most rainfall in Roy. Rain falls for 18.6 days and accumulates 4.96" (126mm) of precipitation.

How many days does it rain in December in Roy?

In December, in Roy, the rain falls for 18.6 days. Throughout December, 4.96" (126mm) of precipitation is accumulated.

How much does it snow in Roy in December?

In Roy, Washington, during December, snow falls for 1.4 days and regularly aggregates up to 0.24" (6mm) of snow.

What is the month with the shortest days in Roy?

December has the shortest days of the year in Roy, Washington, with an average of 8h and 36min of daylight.

How many hours of daylight does Roy have in December?

In December, the average day length is 8h and 35min.

When are sunrise and sunset in December in Roy?

In December, on the first day of the month, sunrise is at 7:36 am and sunset at 4:22 pm. On the last day of the month, in Roy, Washington, sunrise is at 7:55 am and sunset at 4:31 pm PST.

What is the month with the least sunshine in Roy?

December has the least sunshine of the year, with an average of 3.9h of sunshine.

How many hours of sunshine does Roy have in December?

In Roy, the average sunshine duration in December is 3.9h.

What is the month with the lowest UV index in Roy?

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index.

What is the UV index intensity in December in Roy?

The average daily maximum UV index in December in Roy is 2. A UV Index of 2, and less, symbolizes a minimal health vulnerability from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in December
Roy, WA

Average temperature in December - Roy, WA
  • Average high temperature in December: 43.5°F

The warmest month (with the highest average high temperature) is August (78.4°F).
The month with the lowest average high temperature is December (43.5°F).

  • Average low temperature in December: 34.2°F

The month with the highest average low temperature is August (52.2°F).
The coldest month (with the lowest average low temperature) is February (34°F).

Average pressure in December
Roy, WA

Average pressure in December - Roy, WA
  • Average pressure in December: 30.08"Hg

The month with the highest atmospheric pressure is January (30.09"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).

Average wind speed in December
Roy, WA

Average wind speed in December - Roy, WA
  • Average wind speed in December: 4.5mph

The windiest month (with the highest average wind speed) is March (5mph).
The calmest month (with the lowest average wind speed) is August (3.7mph).

Average humidity in December
Roy, WA

Average humidity in December - Roy, WA
  • Average humidity in December: 87%

The month with the highest relative humidity is January (88%).
The month with the lowest relative humidity is July (69%).

Average rainfall in December
Roy, WA

Average rainfall in December - Roy, WA
  • Average rainfall in December: 4.96"

The wettest month (with the highest rainfall) is December (4.96").
The driest month (with the least rainfall) is July (0.35").

Average rainfall days in December
Roy, WA

Average rainfall days in December - Roy, WA
  • Average rainfall days in December: 18.6 days

The month with the highest number of rainy days is March (19.7 days).
The month with the least rainy days is August (5.2 days).

Average snowfall in December
Roy, WA

Average snowfall in December - Roy, WA
  • Average snowfall in December: 0.24"

The month with the highest snowfall is February (1.73").
The months with the least snowfall are May, June, July, August, September and October (0").

Average snowfall days in December
Roy, WA

Average snowfall days in December - Roy, WA
  • Average snowfall days in December: 1.4 days

The month with the highest number of snowfall days is February (2.8 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

Average daylight in December /
Average sunshine in December
Roy, WA

Average daylight in December / Average sunshine in December - Roy, WA
  • Average daylight in December: 8h and 4min

The month with the longest days is June (Average daylight: 15h and 48min).
The month with the shortest days is December (Average daylight: 8h and 36min).

  • Average sunshine in December: 3h and 5min

The month with the most sunshine is August (Average sunshine: 10h and 36min).
The month with the least sunshine is December (Average sunshine: 3h and 54min).

Average sunshine days in December
Roy, WA

Average sunshine days in December - Roy, WA
  • Average sunshine days in December: 10.1 days

The month with the most sunshine days is August (22.9 days).
The month with the least sunshine days is November (9.1 days).

Average UV index in December
Roy, WA

Average UV index in December - Roy, 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
Roy, WA

Average cloud cover in December - Roy, WA
  • Average cloud cover in December: 59

The months with the most cloud cover are January and December (Cloud cover 59).
The months with the least cloud cover are July and August (Cloud cover 28).

Average visibility in December
Roy, WA

Average visibility in December - Roy, WA
  • Average visibility in December: 4mi

The months with the highest visibility are July and August (6mi).
The months with the lowest visibility are January, February and December (4mi).

Roy, Washington, USA

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