May weather forecast
O'Fallon, MO

Weather in May

The last month of the spring, May, is a moderately hot month in O'Fallon, Missouri, with temperature in the range of an average low of 57°F (13.9°C) and an average high of 74.5°F (23.6°C).

Temperature

In May, the average high-temperature rises from an enjoyable 65.3°F (18.5°C) in April to a moderately hot 74.5°F (23.6°C). The average low-temperature, in O'Fallon, is 57°F (13.9°C).

Humidity

The most humid month is May, with an average relative humidity of 79%.

Rainfall

May is the month with the most rainfall. Rain falls for 15.7 days and accumulates 2.76" (70mm) of precipitation.

Snowfall

April through October are months without snowfall.

Daylight

In O'Fallon, the average length of the day in May is 14h and 19min.
On the first day of the month, sunrise is at 6:04 am and sunset at 7:55 pm. On the last day of May, in O'Fallon, sunrise is at 5:39 am and sunset at 8:21 pm CDT.

Sunshine

In O'Fallon, the average sunshine in May is 9.6h.

UV index

The months with the highest UV index are May through August, with an average maximum UV index of 6. A UV Index value of 6 to 7 symbolizes a high health risk from exposure to the Sun's UV rays for average individuals.
Note: The average daily UV index of 6 in May transform into the following instructions:
Take precautions against overexposure. Protection against sun damage is needed. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. 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.
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FAQ

What is the most humid month in O'Fallon?

May is the most humid month in O'Fallon, Missouri, with an average relative humidity of 79%.

What is the average humidity in May in O'Fallon?

The average relative humidity in May is 79%.

What is the wettest month in O'Fallon?

May is the month with the most rainfall. Rain falls for 15.7 days and accumulates 2.76" (70mm) of precipitation.

How many days does it rain in May in O'Fallon?

In O'Fallon, Missouri, during May, the rain falls for 15.7 days and regularly aggregates up to 2.76" (70mm) of precipitation.

When it does not snow in O'Fallon?

In O'Fallon, Missouri, snow does not fall in April through October.

How many hours of daylight does O'Fallon have in May?

In O'Fallon, Missouri, the average day length in May is 14h and 19min.

When is the sunrise / sunset in May in O'Fallon?

In May, on the first day of the month, sunrise is at 6:04 am and sunset at 7:55 pm. On the last day of the month, sunrise is at 5:39 am and sunset at 8:21 pm CDT.

How many hours of sunshine does O'Fallon have in May?

In May, the average sunshine duration is 9.6h.

What is the month with the highest UV index in O'Fallon?

May through August, with an average maximum UV index of 6, are months with the highest UV index in O'Fallon, Missouri.

What is the UV index reading in May in O'Fallon?

In May, the average daily maximum UV index in O'Fallon is 6. A UV Index estimate of 6 to 7 represents a high hazard to health from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in May
O'Fallon, MO

Average temperature in May - O
  • Average high temperature in May: 74.5°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 May: 57°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).

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Average pressure in May
O'Fallon, MO

Average pressure in May - O
  • Average pressure in May: 29.95"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).

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Average wind speed in May
O'Fallon, MO

Average wind speed in May - O
  • Average wind speed in May: 7.2mph

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).

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Average humidity in May
O'Fallon, MO

Average humidity in May - O
  • Average humidity in May: 79%

The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (70%).

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Average rainfall in May
O'Fallon, MO

Average rainfall in May - O
  • Average rainfall in May: 2.76"

The wettest month (with the highest rainfall) is May (2.76").
The driest month (with the least rainfall) is December (0.91").

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Average rainfall days in May
O'Fallon, MO

Average rainfall days in May - O
  • Average rainfall days in May: 15.7 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).

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Average snowfall in May
O'Fallon, MO

Average snowfall in May - O
  • Average snowfall in May: 0"

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").

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Average snowfall days in May
O'Fallon, MO

Average snowfall days in May - O
  • Average snowfall days in May: 0 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).

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Average daylight in May /
Average sunshine in May
O'Fallon, MO

Average daylight in May / Average sunshine in May - O
  • Average daylight in May: 14h and 19min

The month with the longest days is June (Average daylight: 14h and 50min).
The month with the shortest days is December (Average daylight: 9h and 30min).

  • Average sunshine in May: 9h and 36min

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).

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Average sunshine days in May
O'Fallon, MO

Average sunshine days in May - O
  • Average sunshine days in May: 12.9 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).

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Average UV index in May
O'Fallon, MO

Average UV index in May - O
  • Average UV index in May: 6

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).

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Average cloud cover in May
O'Fallon, MO

Average cloud cover in May - O
  • Average cloud cover in May: 36

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).

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Average visibility in May
O'Fallon, MO

Average visibility in May - O
  • Average visibility in May: 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).

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