December weather forecast
Castle Rock, CO

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The scenic setting of Castle Rock City in Colorado
The scenic setting of Castle Rock City in Colorado

Weather in December

December in Castle Rock is the onset of the winter season with temperatures dropping to an average low of 20.1°F (-6.6°C). Compared to November, it’s a much colder month, characterized by the typical winter chills. Snowfall measures about 3.86" (98mm), turning the city into a winter wonderland. The shorter daylight hours and frosty weather signal the full grip of winter. Despite the cold, the holiday spirit combined with the beautiful white scenery makes December an enchanting time in Castle Rock.

Temperature

December, marked by an average high-temperature of 39.6°F (4.2°C) and a low-temperature of 20.1°F (-6.6°C), is the coldest month in Castle Rock.

Humidity

The average relative humidity in December is 62%.

Rainfall

The months with the least rainfall in Castle Rock are January and December Rain falls for 5.5 days and accumulates 0.55" (14mm) of rain.

Snowfall

January through June, October through December are months with snowfall in Castle Rock. In December, in Castle Rock, it is snowing for 8.4 days. Throughout December, 3.86" (98mm) of snow is accumulated. In Castle Rock, during the entire year, snow falls for 51 days and aggregates up to 40.43" (1027mm) of snow.

Daylight

The month with the shortest days is December, with an average of 9h and 24min of daylight.
On the first day of the month, sunrise is at 7:00 am and sunset at 4:36 pm. On the last day of December, sunrise is at 7:19 am and sunset at 4:46 pm MST.

Sunshine

In December, the average sunshine is 7h.

UV index

January, February, October through December, with an average maximum UV index of 2, are months with the lowest UV index in Castle Rock. A UV Index estimate of 2, and below, represents a low threat to health from unsafe exposure to UV radiation for ordinary individuals.
Note: The daily high UV index of 2 during December translates into the following recommendations:
Prolonged sun exposure generally does not trouble most people. However, it is vital to ensure protection for babies, children, and individuals with sensitive skin. The intensity of the Sun's UV radiation during midday suggests reducing time spent outdoors. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays. Take into account! The reflection from snow can nearly double the Sun's UV radiation intensity.
Updated: Feb 10, 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 Castle Rock?

Castle Rock, Colorado, reaches its average lowest temperatures in December, measuring 39.6°F (4.2°C) at the peak and 20.1°F (-6.6°C) at the lowest.

How cold is it in Castle Rock in December?

In Castle Rock, 39.6°F (4.2°C) is the average high-temperature and 20.1°F (-6.6°C) is the average low-temperature during December. The average heat index (a.k.a. 'apparent temperature', 'real feel'), which factors the actual air temperature with the relative humidity, in August is computed to be 82.4°F (28°C).

What is the average humidity in December in Castle Rock?

In December, the average relative humidity in Castle Rock is 62%.

What is the driest month in Castle Rock?

The months with the least rainfall in Castle Rock, Colorado, are January and December Rain falls for 5.5 days and accumulates 0.55" (14mm) of rain.

How many days does it rain in December in Castle Rock?

In Castle Rock, in December, it is raining for 5.5 days, with typically 0.55" (14mm) of accumulated precipitation.

How much does it snow in Castle Rock in December?

In Castle Rock, in December, snow falls for 8.4 days, with typically accumulated 3.86" (98mm) of snow.

What is the month with the shortest days in Castle Rock?

The month with the shortest days in Castle Rock is December, with an average of 9h and 24min of daylight.

How many hours of daylight does Castle Rock have in December?

In Castle Rock, Colorado, the average day length in December is 9h and 27min.

When is the sunrise / sunset in December in Castle Rock?

On the first day of December in Castle Rock, Colorado, sunrise is at 7:00 am and sunset at 4:36 pm. On the last day of the month, sunrise is at 7:19 am and sunset at 4:46 pm MST.

How many hours of sunshine does Castle Rock have in December?

The average sunshine duration in December is 7h.

When is the lowest UV index in Castle Rock?

The months with the lowest UV index in Castle Rock are January, February, October through December, with an average maximum UV index of 2.

What is the UV index reading in December in Castle Rock?

The average daily maximum UV index in December is 2. A UV Index of 2, and less, symbolizes a minimal health vulnerability from unprotected exposure to UV radiation.
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
Castle Rock, CO

Average temperature in December - Castle Rock, CO
  • Average high temperature in December: 39.6°F

The warmest month (with the highest average high temperature) is July (83.3°F).
The month with the lowest average high temperature is December (39.6°F).

  • Average low temperature in December: 20.1°F

The month with the highest average low temperature is July (57.2°F).
The coldest month (with the lowest average low temperature) is December (20.1°F).

Average pressure in December
Castle Rock, CO

Average pressure in December - Castle Rock, CO
  • Average pressure in December: 30.11"Hg

The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are April and June (29.91"Hg).

Average wind speed in December
Castle Rock, CO

Average wind speed in December - Castle Rock, CO
  • Average wind speed in December: 6.8mph

The windiest month (with the highest average wind speed) is April (7.9mph).
The calmest months (with the lowest average wind speed) are July, August and September (6.5mph).

Average humidity in December
Castle Rock, CO

Average humidity in December - Castle Rock, CO
  • Average humidity in December: 62%

The month with the highest relative humidity is February (66%).
The months with the lowest relative humidity are June and September (45%).

Average rainfall in December
Castle Rock, CO

Average rainfall in December - Castle Rock, CO
  • Average rainfall in December: 0.55"

The wettest month (with the highest rainfall) is May (2.24").
The driest months (with the least rainfall) are January and December (0.55").

Average rainfall days in December
Castle Rock, CO

Average rainfall days in December - Castle Rock, CO
  • Average rainfall days in December: 5.5 days

The month with the highest number of rainy days is July (15.1 days).
The month with the least rainy days is November (3 days).

Average snowfall in December
Castle Rock, CO

Average snowfall in December - Castle Rock, CO
  • Average snowfall in December: 3.86"

The month with the highest snowfall is April (7.13").
The months with the least snowfall are July, August and September (0").

Average snowfall days in December
Castle Rock, CO

Average snowfall days in December - Castle Rock, CO
  • Average snowfall days in December: 8.4 days

The month with the highest number of snowfall days is February (9.8 days).
The months with the least snowfall days are July and August (0 days).

Average daylight in December /
Average sunshine in December
Castle Rock, CO

Average daylight in December / Average sunshine in December - Castle Rock, CO
  • Average daylight in December: 9h 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 24min).

  • Average sunshine in December: 7h and 0min

The months with the most sunshine are June, July and August (Average sunshine: 11h and 48min).
The month with the least sunshine is February (Average sunshine: 6h and 48min).

Average sunshine days in December
Castle Rock, CO

Average sunshine days in December - Castle Rock, CO
  • Average sunshine days in December: 20.5 days

The month with the most sunshine days is November (22.8 days).
The month with the least sunshine days is July (10.6 days).

Average UV index in December
Castle Rock, CO

Average UV index in December - Castle Rock, CO
  • Average UV index in December: 2

The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January, February, October, November and December (UV index 2).

Average cloud cover in December
Castle Rock, CO

Average cloud cover in December - Castle Rock, CO
  • Average cloud cover in December: 22

The month with the most cloud cover is April (Cloud cover 27).
The month with the least cloud cover is September (Cloud cover 15).

Average visibility in December
Castle Rock, CO

Average visibility in December - Castle Rock, CO
  • Average visibility in December: 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).

Castle Rock, Colorado, USA

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