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Contents
- Weather in January
- Weather in February
- Weather in March
- Weather in April
- Weather in May
- Weather in June
- Weather in July
- Weather in August
- Weather in September
- Weather in October
- Weather in November
- Weather in December
- Frequently asked questions
- Average temperature
- Average pressure
- Average wind speed
- Average humidity
- Average rainfall
- Average rainfall days
- Average snowfall
- Average snowfall days
- Average daylight
- Average sunshine
- Average sunshine days
- Average UV index
- Average cloud cover
- Average visibility
Weather in January
January, like December, in O'Fallon, Illinois, is another cold winter month, with an average temperature ranging between max 37.8°F (3.2°C) and min 24.6°F (-4.1°C). January, recording an average high temperature of 37.8°F (3.2°C) and a low temperature of 24.6°F (-4.1°C), is O'Fallon's coldest month. Weather in January »
Weather in February
February, the last month of the winter in O'Fallon, is also a wintry month, with an average temperature varying between 27.7°F (-2.4°C) and 42.1°F (5.6°C). The shift into February finds O'Fallon at an average high-temperature of a still wintry 42.1°F (5.6°C), closely comparable to January's conditions. Weather in February »
Weather in March
The first month of the spring, March, is a cool month in O'Fallon, Illinois, with an average temperature varying between 37.9°F (3.3°C) and 54.5°F (12.5°C). Entering March, O'Fallon sees a temperature rise, with the average high-temperature advancing from February's icy 42.1°F (5.6°C) to a fresh 54.5°F (12.5°C). Weather in March »
Weather in April
April in O'Fallon, Illinois, is a refreshing spring month, with temperature in the range of an average low of 47.8°F (8.8°C) and an average high of 64.9°F (18.3°C). As April sets, the average high-temperature shows an increase, moving up from a cool 54.5°F (12.5°C) in March to a comfortable 64.9°F (18.3°C). Weather in April »
Weather in May
May, the last month of the spring in O'Fallon, is a warm month, with an average temperature varying between 57.9°F (14.4°C) and 74.8°F (23.8°C). With the onset of May, O'Fallon's weather sees a temperature rise, transitioning from a comfortable 64.9°F (18.3°C) in April to a warm 74.8°F (23.8°C). Weather in May »
Weather in June
The first month of the summer, June, is also a moderately hot month in O'Fallon, Illinois, with an average temperature ranging between max 83.7°F (28.7°C) and min 66.6°F (19.2°C). June's onset witnesses a minor shift in the average high-temperature, moving from 74.8°F (23.8°C) in May to a still warm 83.7°F (28.7°C). Weather in June »
Weather in July
July, like June, in O'Fallon, Illinois, is another warm summer month, with temperature in the range of an average high of 85.6°F (29.8°C) and an average low of 68.2°F (20.1°C). July stands out as O'Fallon's warmest month, with temperatures ranging between an average high of 85.6°F (29.8°C) and a low of 68.2°F (20.1°C). July's average heat index is calculated to be a very hot 98.6°F (37°C). Weather in July »
Weather in August
August, the last month of the summer in O'Fallon, is another warm month, with an average temperature varying between 66°F (18.9°C) and 84.2°F (29°C). The shift into August uncovers an average high-temperature of a still moderately hot 84.2°F (29°C), subtly different from the previous month. Weather in August »
Weather in September
September, the first month of the autumn in O'Fallon, is still a warm month, with temperature in the range of an average high of 79°F (26.1°C) and an average low of 60.3°F (15.7°C). With September's arrival, O'Fallon notes an average high-temperature of a still moderately hot 79°F (26.1°C), closely following the trend of the preceding month. Weather in September »
Weather in October
October, like September, in O'Fallon, Illinois, is another refreshing autumn month, with an average temperature fluctuating between 66.6°F (19.2°C) and 48.7°F (9.3°C). In O'Fallon, the average high-temperature in October decreases from a moderately hot 79°F (26.1°C) in September to a comfortable 66.6°F (19.2°C). Weather in October »
Weather in November
The last month of the autumn, November, is also a fresh month in O'Fallon, Illinois, with temperature in the range of an average low of 38.1°F (3.4°C) and an average high of 53.1°F (11.7°C). As October transitions into November, O'Fallon sees a drop in the average high-temperature, transitioning from a refreshing 66.6°F (19.2°C) to a fresh 53.1°F (11.7°C). Weather in November »
Weather in December
December, the first month of the winter in O'Fallon, is also an icy month, with an average temperature varying between 30.6°F (-0.8°C) and 42.6°F (5.9°C). December comes with a drop in the average high-temperature, falling from November's fresh 53.1°F (11.7°C) to a cold 42.6°F (5.9°C). Weather in December »
[Resources]Frequently asked questions
What month is the coldest in O'Fallon?
O'Fallon, Illinois, records the coldest temperatures in January, averaging a high of 37.8°F (3.2°C) and a low of 24.6°F (-4.1°C).
How many days does it rain in O'Fallon?
Throughout the year, in O'Fallon, Illinois, there are 108.8 rainfall days, and 10.24" (260mm) of precipitation is accumulated.
When does it snow in O'Fallon?
Months with snowfall in O'Fallon, Illinois, are January through March, November and December.
What is the snowiest month in O'Fallon?
January is the month with the most snowfall in O'Fallon, Illinois. Snow falls for 4.7 days and accumulates 0.51" (13mm) of snow.
How much does it snow in O'Fallon?
In O'Fallon, during the entire year, snow falls for 13.3 days and aggregates up to 1.14" (29mm) of snow.
What is the month with the least sunshine in O'Fallon?
The month with the least sunshine is January, with an average of 4.5h of sunshine.
What is the month with the lowest UV index in O'Fallon?
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index in O'Fallon, Illinois.
When is Daylight Saving Time (DST) in O'Fallon?
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts in O'Fallon, and the time zone changes from CST to CDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from CDT to CST.
When it does not snow in O'Fallon?
April through October are months without snowfall in O'Fallon.
What are the most humid months in O'Fallon?
The months with the highest humidity in O'Fallon, Illinois, are May, July and August, with an average relative humidity of 79%.
When is the highest UV index in O'Fallon?
The months with the highest UV index in O'Fallon are May through August, with an average maximum UV index of 6.
When are the longest days in O'Fallon?
With an average of 14h and 48min of daylight, June has the longest days of the year in O'Fallon.
What is the month with the most sunshine in O'Fallon?
The months with the most sunshine in O'Fallon, Illinois, are June and July, with an average of 10.4h of sunshine.
What month is the hottest in O'Fallon?
July proves to be the warmest month in O'Fallon, Illinois, recording an average peak temperature of 85.6°F (29.8°C) and a minimum temperature of 68.2°F (20.1°C).
What is the wettest month in O'Fallon?
The month with the most rainfall is July, when the rain falls for 13.1 days and typically aggregates up to 1.42" (36mm) of precipitation.
What is the least humid month in O'Fallon?
The least humid month is October, with an average relative humidity of 70%.
What is the driest month in O'Fallon?
December is the month with the least rainfall. Rain falls for 4.6 days and accumulates 0.31" (8mm) of precipitation.
What is the month with the shortest days in O'Fallon?
With an average of 9h and 30min of daylight, December has the shortest days of the year.
Average temperature
O'Fallon, IL
The warmest month (with the highest average high temperature) is July (85.6°F).
The month with the lowest average high temperature is January (37.8°F).
The month with the highest average low temperature is July (68.2°F).
The coldest month (with the lowest average low temperature) is January (24.6°F).
Average pressure
O'Fallon, IL
- Average pressure in January:
30.16"Hg - Average pressure in February:
30.12"Hg - Average pressure in March:
30.07"Hg - Average pressure in April:
29.94"Hg - Average pressure in May:
29.96"Hg - Average pressure in June:
29.93"Hg
- Average pressure in July:
29.97"Hg - Average pressure in August:
29.98"Hg - Average pressure in September:
30.03"Hg - Average pressure in October:
30.04"Hg - Average pressure in November:
30.13"Hg - 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 (29.93"Hg).
Average wind speed
O'Fallon, IL
- Average wind speed in January:
9.5mph - Average wind speed in February:
9.4mph - Average wind speed in March:
9.3mph - Average wind speed in April:
9.1mph - Average wind speed in May:
7.5mph - Average wind speed in June:
6.6mph
- Average wind speed in July:
5.6mph - Average wind speed in August:
5.7mph - Average wind speed in September:
6.2mph - Average wind speed in October:
8.2mph - Average wind speed in November:
8.8mph - Average wind speed in December:
8.9mph
The windiest month (with the highest average wind speed) is January (9.5mph).
The calmest month (with the lowest average wind speed) is July (5.6mph).
Average humidity
O'Fallon, IL
The months with the highest relative humidity are May, July and August (79%).
The month with the lowest relative humidity is October (70%).
Average rainfall
O'Fallon, IL
- Average rainfall in January:
0.71" - Average rainfall in February:
0.47" - Average rainfall in March:
0.71" - Average rainfall in April:
1.1" - Average rainfall in May:
1.34" - Average rainfall in June:
1.14"
- Average rainfall in July:
1.42" - Average rainfall in August:
1.26" - Average rainfall in September:
0.67" - Average rainfall in October:
0.75" - Average rainfall in November:
0.35" - Average rainfall in December:
0.31"
The wettest month (with the highest rainfall) is July (1.42").
The driest month (with the least rainfall) is December (0.31").
Average rainfall days
O'Fallon, IL
- Average rainfall days in January:
4.8 days - Average rainfall days in February:
5.3 days - Average rainfall days in March:
9.7 days - Average rainfall days in April:
12.3 days - Average rainfall days in May:
12.8 days - Average rainfall days in June:
11.1 days
- Average rainfall days in July:
13.1 days - Average rainfall days in August:
11.1 days - Average rainfall days in September:
9.8 days - Average rainfall days in October:
8.3 days - Average rainfall days in November:
5.9 days - Average rainfall days in December:
4.6 days
The month with the highest number of rainy days is July (13.1 days).
The month with the least rainy days is December (4.6 days).
Average snowfall
O'Fallon, IL
The month with the highest snowfall is January (0.51").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days
O'Fallon, IL
- Average snowfall days in January:
4.7 days - Average snowfall days in February:
4 days - Average snowfall days in March:
1.4 days - Average snowfall days in April:
0.1 days - Average snowfall days in May:
0 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0 days - Average snowfall days in October:
0 days - Average snowfall days in November:
0.7 days - Average snowfall days in December:
2.4 days
The month with the highest number of snowfall days is January (4.7 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight / Average sunshine
O'Fallon, IL
- Average daylight in January:
9h and 5min - Average daylight in February:
10h and 5min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 1min - Average daylight in May:
14h and 2min - Average daylight in June:
14h and 5min
- Average daylight in July:
14h and 3min - Average daylight in August:
13h and 4min - Average daylight in September:
12h and 2min - Average daylight in October:
11h and 1min - Average daylight in November:
10h and 1min - Average daylight in December:
9h and 3min
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 January:
4h and 3min - Average sunshine in February:
4h and 4min - Average sunshine in March:
6h and 2min - Average sunshine in April:
8h and 4min - Average sunshine in May:
9h and 2min - Average sunshine in June:
10h and 2min
- Average sunshine in July:
10h and 2min - Average sunshine in August:
10h and 1min - Average sunshine in September:
9h and 2min - Average sunshine in October:
6h and 2min - Average sunshine in November:
5h and 2min - Average sunshine in December:
4h and 4min
The months with the most sunshine are June and July (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 30min).
Average sunshine days
O'Fallon, IL
- Average sunshine days in January:
23.1 days - Average sunshine days in February:
19.6 days - Average sunshine days in March:
18.4 days - Average sunshine days in April:
15.8 days - Average sunshine days in May:
15.5 days - Average sunshine days in June:
16.2 days
- Average sunshine days in July:
15.5 days - Average sunshine days in August:
18 days - Average sunshine days in September:
18.3 days - Average sunshine days in October:
22.2 days - Average sunshine days in November:
22.5 days - Average sunshine days in December:
23.6 days
The month with the most sunshine days is December (23.6 days).
The months with the least sunshine days are May and July (15.5 days).
Average UV index
O'Fallon, IL
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
O'Fallon, IL
The month with the most cloud cover is January (Cloud cover 51).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility
O'Fallon, IL
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).
O'Fallon, Illinois, USA
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