December weather forecast
Hillsboro, OR

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The red tree colors of the fall along a road and amid trees in this tranquil neighborhood in Hillsboro, Oregon
The red tree colors of the fall along a road and amid trees in this tranquil neighborhood in Hillsboro, Oregon

Weather in December

December brings the full force of winter to Hillsboro with an average high temperature of about 43.9°F (6.6°C) and an increase in rainfall to 4.45" (113mm) on average. The dwindling daylight hours, coupled with often cloudy skies and relatively high humidity, underline the chill factor. Subtle snowfall marks the festive season, lending a white veneer to the city, though instances are sparse. Despite the cold, the festive spirit permeates the cityscape, making it an exciting period in Hillsboro. Despite grey, short days, Hillsboro sparkles with holiday lights making winter sightseeing a unique experience.

Temperature

The coldest time of the year is December, with temperatures averaging a high of 43.9°F (6.6°C) and a low of 34°F (1.1°C).

Humidity

January, February, November and December, with an average relative humidity of 85%, are the most humid months.

Rainfall

In Hillsboro, in December, it is raining for 18.8 days, with typically 4.45" (113mm) of accumulated precipitation. In Hillsboro, during the entire year, the rain falls for 173 days and collects up to 29.49" (749mm) of precipitation.

Snowfall

Months with snowfall are January through March, November and December. In Hillsboro, during December, snow falls for 0.7 days and regularly aggregates up to 0.35" (9mm) of snow. Throughout the year, there are 6.6 snowfall days, and 4.53" (115mm) of snow is accumulated.

Daylight

With an average of 8h and 48min of daylight, December has the shortest days of the year.
On the first day of December, sunrise is at 7:32 am and sunset at 4:30 pm. On the last day of the month, sunrise is at 7:51 am and sunset at 4:38 pm PST.

Sunshine

In December, the average sunshine is 3.9h.

UV index

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Hillsboro. A UV Index estimate of 2, and below, represents a minimal health vulnerability from unprotected exposure to Sun's UV rays for the ordinary person.
Note: In December, the maximum UV index of 2 suggests these recommendations:
Despite the majority tolerating prolonged sun exposure, those with sensitive skin, infants, and children demand continual protection. The solar radiation around mid-day is intense; avoid the Sun and stay safe. Clothes that are both tight-knit and comfortably loose are prime choices for sun protection. Be prepared! The intensity of the Sun's UV radiation can be amplified nearly double due to snow reflection.
Updated: Jun 16, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What part of the year is the coldest?

December is the coldest month, with the temperature often reaching an average high of 43.9°F (6.6°C) and an average low of 34°F (1.1°C).

How cold does it get in December?

The high-temperature, in December, in Hillsboro, records 43.9°F (6.6°C), while the low-temperature is 34°F (1.1°C). In August, the average heat index (a.k.a. 'feels like', 'apparent temperature'), which combines relative humidity and air temperature, is appraised at 84.2°F (29°C).

What is the most humid month?

January, February, November and December, with an average relative humidity of 85%, are most humid months.

What is the average humidity in December?

The average relative humidity in December is 85%.

How many days does it rain in December?

In Hillsboro, during December, the rain falls for 18.8 days and regularly aggregates up to 4.45" (113mm) of precipitation.

How many days does it snow in December?

In December, it is snowing for 0.7 days. Throughout December, 0.35" (9mm) of snow is accumulated.

What is the month with the shortest days?

The month with the shortest days is December, with an average of 8h and 48min of daylight.

How many hours of daylight does Hillsboro have in December?

The average day length in December is 8h and 46min.

When are sunrise and sunset in December?

On the first day of December in Hillsboro, Oregon, sunrise is at 7:32 am and sunset at 4:30 pm. On the last day of the month, sunrise is at 7:51 am and sunset at 4:38 pm PST.

How long on average sun shines in December?

The average sunshine duration in December is 3.9h.

When is the lowest UV index?

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

What is the UV index intensity in December?

In Hillsboro, the average daily maximum UV index in December is 2. A UV Index estimate of 2, and below, represents a low health threat 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
Hillsboro, OR

Average temperature in December - Hillsboro, OR
  • Average high temperature in December: 43.9°F

The warmest month (with the highest average high temperature) is August (81.5°F).
The month with the lowest average high temperature is December (43.9°F).

  • Average low temperature in December: 34°F

The month with the highest average low temperature is August (55.4°F).
The coldest month (with the lowest average low temperature) is December (34°F).

Average pressure in December
Hillsboro, OR

Average pressure in December - Hillsboro, OR
  • Average pressure in December: 30.1"Hg

The month with the highest atmospheric pressure is January (30.11"Hg).
The months with the lowest atmospheric pressure are August and September (30.01"Hg).

Average wind speed in December
Hillsboro, OR

Average wind speed in December - Hillsboro, OR
  • Average wind speed in December: 4.7mph

The windiest month (with the highest average wind speed) is March (5mph).
The calmest months (with the lowest average wind speed) are June, August and September (4.3mph).

Average humidity in December
Hillsboro, OR

Average humidity in December - Hillsboro, OR
  • Average humidity in December: 85%

The months with the highest relative humidity are January, February, November and December (85%).
The month with the lowest relative humidity is August (64%).

Average rainfall in December
Hillsboro, OR

Average rainfall in December - Hillsboro, OR
  • Average rainfall in December: 4.45"

The wettest month (with the highest rainfall) is January (4.57").
The driest month (with the least rainfall) is August (0.31").

Average rainfall days in December
Hillsboro, OR

Average rainfall days in December - Hillsboro, OR
  • Average rainfall days in December: 18.8 days

The month with the highest number of rainy days is March (20.8 days).
The month with the least rainy days is August (4.4 days).

Average snowfall in December
Hillsboro, OR

Average snowfall in December - Hillsboro, OR
  • Average snowfall in December: 0.35"

The month with the highest snowfall is February (1.81").
The months with the least snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in December
Hillsboro, OR

Average snowfall days in December - Hillsboro, OR
  • Average snowfall days in December: 0.7 days

The month with the highest number of snowfall days is February (2.4 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
Hillsboro, OR

Average daylight in December / Average sunshine in December - Hillsboro, OR
  • Average daylight in December: 8h and 5min

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

  • 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 February (Average sunshine: 3h and 42min).

Average sunshine days in December
Hillsboro, OR

Average sunshine days in December - Hillsboro, OR
  • Average sunshine days in December: 10.5 days

The month with the most sunshine days is July (24.4 days).
The month with the least sunshine days is March (8.5 days).

Average UV index in December
Hillsboro, OR

Average UV index in December - Hillsboro, OR
  • 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
Hillsboro, OR

Average cloud cover in December - Hillsboro, OR
  • Average cloud cover in December: 60

The month with the most cloud cover is February (Cloud cover 63).
The month with the least cloud cover is August (Cloud cover 25).

Average visibility in December
Hillsboro, OR

Average visibility in December - Hillsboro, OR
  • Average visibility in December: 5mi

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

Hillsboro, Oregon, USA

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