December Weather in Crater Lake National Park United States

Daily high temperatures decrease by 3°F, from 41°F to 38°F, rarely falling below 28°F or exceeding 51°F. The lowest daily average high temperature is 38°F on December 25.

Daily low temperatures decrease by 3°F, from 25°F to 22°F, rarely falling below 9°F or exceeding 36°F. The lowest daily average low temperature is 22°F on December 22.

For reference, on August 3, the hottest day of the year, temperatures in Crater Lake National Park typically range from 51°F to 85°F, while on December 22, the coldest day of the year, they range from 22°F to 38°F.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on December. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

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The month of December in Crater Lake National Park experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 65% throughout the month.

The clearest day of the month is December 12, with clear, mostly clear, or partly cloudy conditions 36% of the time.

For reference, on January 10, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 66%, while on August 2, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 87%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Crater Lake National Park, the chance of a wet day over the course of December is decreasing, starting the month at 33% and ending it at 27%.

For reference, the year's highest daily chance of a wet day is 33% on December 6, and its lowest chance is 4% on August 3.

Over the course of December in Crater Lake National Park, the chance of a day with only rain decreases from 21% to 14%, the chance of a day with mixed snow and rain remains an essentially constant 8% throughout, and the chance of a day with only snow increases from 3% to 6%.

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during December in Crater Lake National Park is gradually decreasing, starting the month at 2.4 inches, when it rarely exceeds 4.9 inches or falls below 0.4 inches, and ending the month at 2.1 inches, when it rarely exceeds 5.2 inches or falls below 0.2 inches.

The highest average 31-day accumulation is 2.4 inches on December 8.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during December in Crater Lake National Park is gradually increasing, starting the month at 4.5 inches, when it rarely exceeds 11.4 inches or falls below 0.3 inches, and ending the month at 5.4 inches, when it rarely exceeds 15.2 inches or falls below 0.1 inches.

The highest average 31-day accumulation is 5.6 inches on December 21.

Over the course of December in Crater Lake National Park, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 1 minute of daylight and the longest day is December 1, with 9 hours, 14 minutes of daylight.

The earliest sunrise of the month in Crater Lake National Park is 7:20 AM on December 1 and the latest sunrise is 19 minutes later at 7:39 AM on December 31.

The earliest sunset is 4:33 PM on December 8 and the latest sunset is 10 minutes later at 4:44 PM on December 31.

Daylight saving time is observed in Crater Lake National Park during 2024, but it neither starts nor ends during December, so the entire month is in daylight saving time.

For reference, on June 20, the longest day of the year, the Sun rises at 5:29 AM and sets 15 hours, 21 minutes later, at 8:51 PM, while on December 21, the shortest day of the year, it rises at 7:36 AM and sets 9 hours, 1 minute later, at 4:37 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for December 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Crater Lake National Park is essentially constant during December, remaining around 0% throughout.

For reference, on July 8, the muggiest day of the year, there are muggy conditions 0% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Crater Lake National Park is essentially constant during December, remaining within 0.1 miles per hour of 6.8 miles per hour throughout.

For reference, on March 15, the windiest day of the year, the daily average wind speed is 7.1 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 5.0 miles per hour.

The hourly average wind direction in Crater Lake National Park throughout December is predominantly from the south, with a peak proportion of 43% on December 15.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Crater Lake National Park typically lasts for 3.7 months (112 days), from around June 2 to around September 22, rarely starting before May 14 or after June 21, and rarely ending before September 2 or after October 10.

The month of December in Crater Lake National Park is reliably fully outside of the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Crater Lake National Park are essentially constant during December, remaining around 2,099°F throughout.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Crater Lake National Park is essentially constant during December, remaining within 0.1 kWh of 1.7 kWh throughout.

The lowest average daily incident shortwave solar energy during December is 1.7 kWh on December 15.

For the purposes of this report, the geographical coordinates of Crater Lake National Park are 42.941 deg latitude, -122.133 deg longitude, and 0 ft elevation.

The topography within 2 miles of Crater Lake National Park is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet).

The area within 2 miles of Crater Lake National Park is covered by water (82%), within 10 miles by trees (86%), and within 50 miles by trees (62%) and shrubs (32%).