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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 Williamson, Illinois, is a wintry winter month, with an average temperature varying between 35.6°F (2°C) and 22.6°F (-5.2°C). In Williamson, January is the coldest month, with temperatures averaging a high of 35.6°F (2°C) and a low of 22.6°F (-5.2°C). Weather in January »
Weather in February
The last month of the winter, February, is also a wintry month in Williamson, Illinois, with an average temperature fluctuating between 40.6°F (4.8°C) and 26.4°F (-3.1°C). With the onset of February, the average high-temperature registers at a still icy 40.6°F (4.8°C), subtly different from January's 35.6°F (2°C). Weather in February »
Weather in March
March, the first month of the spring in Williamson, is a fresh month, with an average temperature fluctuating between 36.9°F (2.7°C) and 52.3°F (11.3°C). March brings a rise in Williamson's average high-temperature, moving from an icy 40.6°F (4.8°C) in February to a fresh 52.3°F (11.3°C). Weather in March »
Weather in April
April is a comfortable spring month in Williamson, Illinois, with an average temperature fluctuating between 46.6°F (8.1°C) and 63.9°F (17.7°C). April's onset brings a temperature rise, moving from a fresh 52.3°F (11.3°C) in March to an enjoyable 63.9°F (17.7°C). Weather in April »
Weather in May
The last month of the spring, May, is a moderately hot month in Williamson, Illinois, with an average temperature varying between 73.9°F (23.3°C) and 56.7°F (13.7°C). The shift into May is accompanied by a temperature increase, with the average high-temperature rising from an enjoyable 63.9°F (17.7°C) in April to a warm 73.9°F (23.3°C). Weather in May »
Weather in June
The first month of the summer, June, is also a moderately hot month in Williamson, Illinois, with an average temperature fluctuating between 82.2°F (27.9°C) and 65.5°F (18.6°C). June signifies a subtle uplift in the average high-temperature, adjusting from a moderately hot 73.9°F (23.3°C) in May to a still warm 82.2°F (27.9°C). Weather in June »
Weather in July
July, like June, in Williamson, Illinois, is another warm summer month, with an average temperature fluctuating between 67.5°F (19.7°C) and 84.2°F (29°C). In Williamson, July is the warmest month, with temperatures averaging a high of 84.2°F (29°C) and a low of 67.5°F (19.7°C). For most parts of July, the heat index is computed to be a torrid 95°F (35°C). Weather in July »
Weather in August
August, the last month of the summer in Williamson, is another warm month, with an average temperature ranging between min 65.5°F (18.6°C) and max 82.9°F (28.3°C). The advent of August reveals an average high-temperature of a still warm 82.9°F (28.3°C), showing minimal difference from the prior month. Weather in August »
Weather in September
The first month of the autumn, September, is also a moderately hot month in Williamson, Illinois, with an average temperature fluctuating between 77.9°F (25.5°C) and 59.4°F (15.2°C). Williamson, Illinois, observes an average high-temperature of a still warm 77.9°F (25.5°C) in September, barely different from 82.9°F (28.3°C) in August. Weather in September »
Weather in October
October, the same as September, is another enjoyable autumn month in Williamson, Illinois, with an average temperature ranging between min 48.4°F (9.1°C) and max 65.3°F (18.5°C). In Williamson, entering October brings a temperature decrement, reducing from September's warm 77.9°F (25.5°C) to a comfortable 65.3°F (18.5°C). Weather in October »
Weather in November
November, the last month of the autumn in Williamson, is another cool month, with an average temperature fluctuating between 51.6°F (10.9°C) and 36.9°F (2.7°C). The commencement of November indicates a shift in the average high-temperature, receding from October's comfortable 65.3°F (18.5°C) to a fresh 51.6°F (10.9°C). Weather in November »
Weather in December
December, the first month of the winter in Williamson, is still a cold month, with temperature in the range of an average high of 40.3°F (4.6°C) and an average low of 29.1°F (-1.6°C). December is characterized by a reduction in the average high-temperature, from a fresh 51.6°F (10.9°C) in November to a cold 40.3°F (4.6°C). Weather in December »
Updated: Aug 8, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the coldest month?
Williamson, Illinois, notes the coldest temperatures in January, with a average high of 35.6°F (2°C) and a low of 22.6°F (-5.2°C).
How much does it rain?
In Williamson, during the entire year, the rain falls for 121.4 days and collects up to 14.72" (374mm) of precipitation.
When does it snow?
January through March, November and December are months with snowfall.
How much does it snow?
Throughout the year, there are 19.8 snowfall days, and 2.91" (74mm) of snow is accumulated.
What is the month with the least sunshine?
With an average of 4.4h of sunshine, January has the least sunshine of the year.
What are the months with the lowest UV index?
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index.
What is the driest month?
February is the month with the least rainfall. Rain falls for 5.9 days and accumulates 0.67" (17mm) of precipitation.
When is Daylight Saving Time (DST)?
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts, 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 Williamson, snow does not fall in April through October.
What is the rainiest month?
The month with the most rainfall in Williamson is June, when the rain falls for 13.4 days and typically aggregates up to 1.89" (48mm) of precipitation.
When are the longest days?
The month with the longest days is June, with an average of 14h and 54min of daylight.
What are the months with the most sunshine?
The months with the most sunshine are June and July, with an average of 10.3h of sunshine.
When is the highest UV index?
The months with the highest UV index are June through August, with an average maximum UV index of 6.
What is the warmest month?
July, marked by an average high-temperature of 84.2°F (29°C) and a low-temperature of 67.5°F (19.7°C), is the warmest month.
What is the most humid month?
July is the most humid month, with an average relative humidity of 81%.
What is the least humid month?
With an average relative humidity of 71%, October is the least humid month.
What is the snowiest month?
December is the month with the most snowfall. Snow falls for 3.8 days and accumulates 0.98" (25mm) of snow.
What is the month with the shortest days in Williamson?
With an average of 9h and 30min of daylight, December has the shortest days of the year.
Average temperature
Williamson, IL
The warmest month (with the highest average high temperature) is July (84.2°F).
The month with the lowest average high temperature is January (35.6°F).
The month with the highest average low temperature is July (67.5°F).
The coldest month (with the lowest average low temperature) is January (22.6°F).
Average pressure
Williamson, 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:
29.95"Hg - Average pressure in June:
29.92"Hg
- Average pressure in July:
29.97"Hg - Average pressure in August:
29.98"Hg - Average pressure in September:
30.02"Hg - Average pressure in October:
30.03"Hg - Average pressure in November:
30.12"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 (29.92"Hg).
Average wind speed
Williamson, IL
- Average wind speed in January:
10mph - Average wind speed in February:
9.9mph - Average wind speed in March:
9.6mph - Average wind speed in April:
9.6mph - Average wind speed in May:
7.8mph - Average wind speed in June:
6.8mph
- Average wind speed in July:
5.8mph - Average wind speed in August:
5.9mph - Average wind speed in September:
6.4mph - Average wind speed in October:
8.5mph - Average wind speed in November:
9.2mph - Average wind speed in December:
9.3mph
The windiest month (with the highest average wind speed) is January (10mph).
The calmest month (with the lowest average wind speed) is July (5.8mph).
Average humidity
Williamson, IL
The month with the highest relative humidity is July (81%).
The month with the lowest relative humidity is October (71%).
Average rainfall
Williamson, IL
- Average rainfall in January:
1.02" - Average rainfall in February:
0.67" - Average rainfall in March:
1.02" - Average rainfall in April:
1.57" - Average rainfall in May:
1.81" - Average rainfall in June:
1.89"
The wettest month (with the highest rainfall) is June (1.89").
The driest month (with the least rainfall) is February (0.67").
Average rainfall days
Williamson, IL
- Average rainfall days in January:
5.8 days - Average rainfall days in February:
5.9 days - Average rainfall days in March:
10.7 days - Average rainfall days in April:
12.5 days - Average rainfall days in May:
13.9 days - Average rainfall days in June:
13.4 days
- Average rainfall days in July:
14 days - Average rainfall days in August:
12.1 days - Average rainfall days in September:
10.4 days - Average rainfall days in October:
8.5 days - Average rainfall days in November:
7.5 days - Average rainfall days in December:
6.7 days
The month with the highest number of rainy days is July (14 days).
The month with the least rainy days is January (5.8 days).
Average snowfall
Williamson, IL
The month with the highest snowfall is December (0.98").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days
Williamson, IL
- Average snowfall days in January:
6.3 days - Average snowfall days in February:
5.5 days - Average snowfall days in March:
2.5 days - Average snowfall days in April:
0.3 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:
0.1 days - Average snowfall days in November:
1.3 days - Average snowfall days in December:
3.8 days
The month with the highest number of snowfall days is January (6.3 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight / Average sunshine
Williamson, 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 2min - Average daylight in May:
14h and 2min - Average daylight in June:
14h and 5min
- Average daylight in July:
14h and 4min - 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 54min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in January:
4h and 2min - Average sunshine in February:
4h and 3min - Average sunshine in March:
6h and 2min - Average sunshine in April:
8h and 2min - 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:
9h and 5min - Average sunshine in September:
9h and 2min - Average sunshine in October:
6h and 1min - Average sunshine in November:
5h and 3min - Average sunshine in December:
4h and 5min
The months with the most sunshine are June and July (Average sunshine: 10h and 18min).
The month with the least sunshine is January (Average sunshine: 4h and 24min).
Average sunshine days
Williamson, IL
- Average sunshine days in January:
20.9 days - Average sunshine days in February:
17.2 days - Average sunshine days in March:
17 days - Average sunshine days in April:
14.6 days - Average sunshine days in May:
13.6 days - Average sunshine days in June:
12.8 days
- Average sunshine days in July:
12.5 days - Average sunshine days in August:
15.3 days - Average sunshine days in September:
17.2 days - Average sunshine days in October:
19.7 days - Average sunshine days in November:
20.4 days - Average sunshine days in December:
20.5 days
The month with the most sunshine days is January (20.9 days).
The month with the least sunshine days is July (12.5 days).
Average UV index
Williamson, IL
The months with the highest UV index are 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
Williamson, IL
The month with the most cloud cover is January (Cloud cover 52).
The months with the least cloud cover are June, July, August and September (Cloud cover 29).
Average visibility
Williamson, 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).
Williamson, Illinois, USA
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