December weather forecast
Westmont, IL

Share

Weather in December

The first month of the winter, December, is also an icy month in Westmont, Illinois, with an average temperature varying between 34.5°F (1.4°C) and 25°F (-3.9°C).

Temperature

Westmont in December experiences a subtle temperature decline, with average high-temperatures reducing from a frosty 45.7°F (7.6°C) in November to an icy 34.5°F (1.4°C). Westmont's temperature drops to an average low of 25°F (-3.9°C) during the nights of December.

Humidity

In December, the average relative humidity is 81%.

Rainfall

The month with the least rainfall is December, when the rain falls for 4.9 days and typically collects 0.63" (16mm) of precipitation.

Snowfall

Months with snowfall are January through April, October through December. In Westmont, Illinois, during December, snow falls for 7.2 days and regularly aggregates up to 0.75" (19mm) of snow. In Westmont, during the entire year, snow falls for 34.9 days and aggregates up to 7.2" (183mm) of snow.

Daylight

With an average of 9h and 12min of daylight, December has the shortest days of the year.
On the first day of the month, sunrise is at 7:00 am and sunset at 4:21 pm. On the last day of December, sunrise is at 7:19 am and sunset at 4:31 pm CST.

Sunshine

In December, the average sunshine is 4.1h.

UV index

The average daily maximum UV index in December in Westmont is 2. A UV Index of 2, and less, symbolizes a low threat to health from unsafe exposure to UV radiation for the ordinary person.
Note: An average UV index of 2 in December transforms into this advice:
Babies, children, and individuals with sensitive skin should always have protection against extended sun exposure. Sun exposure should be minimized, especially during midday, to avoid harmful UV radiation. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Mark this! Snow reflection can nearly double the UV radiation intensity from the Sun.
Updated: Aug 17, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

How cold is it in December?

The average high-temperature, in December, in Westmont, is 34.5°F (1.4°C), while the average low-temperature is 25°F (-3.9°C). In August, the average heat index (a.k.a. 'felt air temperature', 'real feel'), which factors the actual air temperature with the relative humidity, is computed to be 86°F (30°C).

What is the average humidity in December?

In December, the average relative humidity is 81%.

What is the driest month?

December is the month with the least rainfall. Rain falls for 4.9 days and accumulates 0.63" (16mm) of precipitation.

How many days does it rain in December in Westmont?

In Westmont, in December, it is raining for 4.9 days, with typically 0.63" (16mm) of accumulated precipitation.

How many days does it snow in December?

In Westmont, during December, snow falls for 7.2 days and regularly aggregates up to 0.75" (19mm) of snow.

What is the month with the shortest days?

December has the shortest days of the year, with an average of 9h and 12min of daylight.

How many hours of daylight does Westmont have in December?

In December, the average day length in Westmont is 9h and 12min.

When are sunrise and sunset in December?

On the first day of December, sunrise is at 7:00 am and sunset at 4:21 pm. On the last day of the month, sunrise is at 7:19 am and sunset at 4:31 pm CST.

How long on average sun shines in December?

In December, the average sunshine duration is 4.1h.

How high is the UV index in December?

In December, the average daily maximum UV index is 2. A UV Index value of 2, and less, symbolizes a minimal health vulnerability from exposure to the Sun's 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
Westmont, IL

Average temperature in December - Westmont, IL
  • Average high temperature in December: 34.5°F

The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (28.8°F).

  • Average low temperature in December: 25°F

The month with the highest average low temperature is July (66.4°F).
The coldest month (with the lowest average low temperature) is January (17.1°F).

Average pressure in December
Westmont, IL

Average pressure in December - Westmont, IL
  • Average pressure in December: 30.09"Hg

The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

Average wind speed in December
Westmont, IL

Average wind speed in December - Westmont, IL
  • Average wind speed in December: 9mph

The windiest month (with the highest average wind speed) is January (9.7mph).
The calmest month (with the lowest average wind speed) is August (6.1mph).

Average humidity in December
Westmont, IL

Average humidity in December - Westmont, IL
  • Average humidity in December: 81%

The months with the highest relative humidity are January and February (82%).
The month with the lowest relative humidity is October (72%).

Average rainfall in December
Westmont, IL

Average rainfall in December - Westmont, IL
  • Average rainfall in December: 0.63"

The wettest month (with the highest rainfall) is May (1.97").
The driest month (with the least rainfall) is December (0.63").

Average rainfall days in December
Westmont, IL

Average rainfall days in December - Westmont, IL
  • Average rainfall days in December: 4.9 days

The month with the highest number of rainy days is May (14.9 days).
The month with the least rainy days is February (4.2 days).

Average snowfall in December
Westmont, IL

Average snowfall in December - Westmont, IL
  • Average snowfall in December: 0.75"

The month with the highest snowfall is February (2.28").
The months with the least snowfall are May, June, July, August and September (0").

Average snowfall days in December
Westmont, IL

Average snowfall days in December - Westmont, IL
  • Average snowfall days in December: 7.2 days

The month with the highest number of snowfall days is January (9.7 days).
The months with the least snowfall days are June, July, August and September (0 days).

Average daylight in December /
Average sunshine in December
Westmont, IL

Average daylight in December / Average sunshine in December - Westmont, IL
  • Average daylight in December: 9h and 1min

The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).

  • Average sunshine in December: 4h and 1min

The month with the most sunshine is August (Average sunshine: 10h and 0min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).

Average sunshine days in December
Westmont, IL

Average sunshine days in December - Westmont, IL
  • Average sunshine days in December: 20.7 days

The month with the most sunshine days is December (20.7 days).
The month with the least sunshine days is July (11.8 days).

Average UV index in December
Westmont, IL

Average UV index in December - Westmont, IL
  • Average UV index in December: 2

The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is January (UV index 1).

Average cloud cover in December
Westmont, IL

Average cloud cover in December - Westmont, IL
  • Average cloud cover in December: 59

The month with the most cloud cover is January (Cloud cover 61).
The month with the least cloud cover is August (Cloud cover 31).

Average visibility in December
Westmont, IL

Average visibility in December - Westmont, IL
  • 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).

Westmont, Illinois, USA

Weather forecast for your location

1. Click Locate me button
2. Allow the app to use your location