December weather forecastO'Fallon, MO
December
Weather in December
December declares the onset of winter as O'Fallon, Missouri grapples with a sharp decline in temperature compared to November. The shortened daylight hours and reduced sunshine hours cast a wintry ambiance over the city. Rainfall maintains a low figure at 0.91" (23mm) with only 7 rainy days recorded on average in the month. Despite the UV index being the lowest in the year, the reflective nature of snow surfaces warrants the usage of eyewear for comfort. A striking feature is the return of snow after a prolonged absence, with 0.67" (17mm) recorded, thereby offering a white Christmas to its inhabitants.Temperature
A shift in the average high-temperature occurs in December, reducing from a fresh 53.2°F (11.8°C) in November to an icy 41.9°F (5.5°C). During the nights in December, the temperature in O'Fallon averages to a subzero cold 30.4°F (-0.9°C).Humidity
In December, the average relative humidity is 76%.Rainfall
December is the month with the least rainfall. Rain falls for 7 days and accumulates 0.91" (23mm) of precipitation.Snowfall
January through March, November and December are months with snowfall. In O'Fallon, during December, snow falls for 3.9 days and regularly aggregates up to 0.67" (17mm) of snow. Throughout the year, there are 19 snowfall days, and 4.13" (105mm) of snow is accumulated.Daylight
The month with the shortest days is December, with an average of 9h and 30min of daylight.On the first day of the month, sunrise is at 7:02 am and sunset at 4:41 pm. On the last day of December, sunrise is at 7:20 am and sunset at 4:51 pm CST.
Sunshine
In O'Fallon, Missouri, the average sunshine in December is 4.8h.UV index
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index. A UV Index value of 2, and less, symbolizes a low threat to health from unsafe exposure to UV radiation for ordinary individuals.Note: A maximum daily UV index of 2 during December morphs into the following directions:
Most individuals can handle sun exposure for up to an hour without burning, but children must always be shielded from sun exposure. Avoiding direct sunlight during midday hours helps reduce the risk from intense UV radiation. Your best bet for sun defense on the face, eyes, and neck is a hat with a wide brim. Remember! The Sun's UV radiation can be magnified almost twofold by the reflection of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
O'Fallon, MO
- Average high temperature in December: 41.9°F
The warmest month (with the highest average high temperature) is July (87.1°F).
The month with the lowest average high temperature is January (37.4°F).
- Average low temperature in December: 30.4°F
The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (23.7°F).
Average pressure in December
O'Fallon, MO
- Average pressure in December: 30.13"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in December
O'Fallon, MO
- Average wind speed in December: 8.6mph
The windiest month (with the highest average wind speed) is January (9.1mph).
The calmest month (with the lowest average wind speed) is July (5.5mph).
Average humidity in December
O'Fallon, MO
- Average humidity in December: 76%
The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (70%).
Average rainfall in December
O'Fallon, MO
- Average rainfall in December: 0.91"
The wettest month (with the highest rainfall) is May (2.76").
The driest month (with the least rainfall) is December (0.91").
Average rainfall days in December
O'Fallon, MO
- Average rainfall days in December: 7 days
The month with the highest number of rainy days is May (15.7 days).
The month with the least rainy days is February (6.8 days).
Average snowfall in December
O'Fallon, MO
- Average snowfall in December: 0.67"
The month with the highest snowfall is February (1.61").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in December
O'Fallon, MO
- Average snowfall days in December: 3.9 days
The months with the highest number of snowfall days are January and February (5.8 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
O'Fallon, MO
- Average daylight in December: 9h and 30min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in December: 4h and 48min
The month with the most sunshine is June (Average sunshine: 10h and 30min).
The months with the least sunshine are January and February (Average sunshine: 4h and 42min).
Average sunshine days in December
O'Fallon, MO
- Average sunshine days in December: 20.6 days
The month with the most sunshine days is December (20.6 days).
The month with the least sunshine days is July (12.6 days).
Average UV index in December
O'Fallon, MO
- Average UV index in December: 2
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in December
O'Fallon, MO
- Average cloud cover in December: 47
The month with the most cloud cover is January (Cloud cover 50).
The months with the least cloud cover are June, July, August and September (Cloud cover 28).
Average visibility in December
O'Fallon, MO
- 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).
