May weather forecast and climate
Decatur, IL

Weather in May

May, the last month of the spring, in Decatur, is a pleasant month, with average temperature varying between 56.7°F (13.7°C) and 72.9°F (22.7°C).

Temperature

In Decatur, the average high-temperature in May rises, from a comfortable 61.9°F (16.6°C) in April, to a pleasant 72.9°F (22.7°C). The average low-temperature, in Decatur, is 56.7°F (13.7°C).

Humidity

In Decatur, the average relative humidity is 77%.

Rainfall

May is the month with the most rainfall in Decatur, Illinois. Rain falls for 17 days and accumulates 2.01" (51mm) of precipitation.

Snowfall

May through October are months without snowfall in Decatur.

Daylight

The average length of the day in Decatur, Illinois, is 14.4h.

Sunshine

The average sunshine in May is 9.3h.

UV index

In Decatur, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a moderate threat to health from the exposure to the Sun's UV radiation for average individuals.
Note: The average daily UV index of 5 in May transform into the following instructions:
Take precautions - Protection against sunburn is recommended. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.
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FAQ

What is the average humidity in May in Decatur?

The average relative humidity in May in Decatur, Illinois, is 77%.

What is the wettest month in Decatur?

May is the month with the most rainfall in Decatur, Illinois. Rain falls for 17 days and accumulates 2.01" (51mm) of precipitation.

How much does it rain in Decatur in May?

In Decatur, in May, during 17 rainfall days, 2.01" (51mm) of precipitation is typically accumulated.

When it does not snow in Decatur?

In Decatur, Illinois, snow does not fall in May through October.

Does it snow in Decatur in May?

In May, in Decatur, Illinois, it doesn't snow. April is the latest month when it typically snows.

What is the average length of the day in May in Decatur?

In May, the average length of the day in Decatur, Illinois, is 14.4h.

How many hours of sunshine does Decatur have in May?

The average sunshine in May in Decatur is 9.3h.

How high is the UV index in May in Decatur?

In Decatur, the average daily maximum UV index in May is 5. A UV Index estimate of 3 to 5 represents a medium health risk from unprotected exposure to the UV radiation.

Average temperature in May
Decatur, IL

Average temperature in May - Decatur, IL
  • Average high temperature in May: 72.9°F

The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (32.9°F).

  • Average low temperature in May: 56.7°F

The month with the highest average low temperature is July (65.7°F).
The coldest month (with the lowest average low temperature) is January (21.2°F).

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Average pressure in May
Decatur, IL

Average pressure in May - Decatur, IL
  • Average pressure in May: 29.96"

The month with the highest atmospheric pressure is January (30.15").
The month with the lowest atmospheric pressure is June (29.92").

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Average wind speed in May
Decatur, IL

Average wind speed in May - Decatur, IL
  • Average wind speed in May: 8.8mph

The windiest month (with the highest average wind speed) is January (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (6.3mph).

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Average humidity in May
Decatur, IL

Average humidity in May - Decatur, IL
  • Average humidity in May: 77%

The month with the highest relative humidity is July (84%).
The month with the lowest relative humidity is October (70%).

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Average rainfall in May
Decatur, IL

Average rainfall in May - Decatur, IL
  • Average rainfall in May: 2.01"

The wettest month (with the highest rainfall) is May (2.01").
The driest months (with the least rainfall) are February and December (0.87").

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Average rainfall days in May
Decatur, IL

Average rainfall days in May - Decatur, IL
  • Average rainfall days in May: 17 days

The month with the highest number of rainy days is May (17 days).
The month with the least rainy days is February (5.8 days).

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Average snowfall in May
Decatur, IL

Average snowfall in May - Decatur, IL
  • Average snowfall in May: 0"

The month with the highest snowfall is January (1.85").
Months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in May
Decatur, IL

Average snowfall days in May - Decatur, IL
  • Average snowfall days in May: 0 days

The month with the highest number of snowfall days is January (7.2 days).
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
Decatur, IL

Average daylight in May / Average sunshine in May - Decatur, IL
  • Average daylight in May: 14.4h

The month with the longest days is June (Average daylight: 15h).
The month with the shortest days is December (Average daylight: 9.4h).

  • Average sunshine in May: 9.3h

The month with the most sunshine is June (Average sunshine: 10.4h).
The month with the least sunshine is January (Average sunshine: 4.1h).

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Average sunshine days in May
Decatur, IL

Average sunshine days in May - Decatur, IL
  • Average sunshine days in May: 11.5 days

The month with the most sunshine days is October (19.8 days).
The month with the least sunshine days is May (11.5 days).

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Average UV index in May
Decatur, IL

Average UV index in May - Decatur, IL
  • Average UV index in May: 5

Months with the highest UV index are June, July and August (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in May
Decatur, IL

Average cloud cover in May - Decatur, IL
  • Average cloud cover in May: 39

The month with the most cloud cover is January (Cloud cover 56).
The month with the least cloud cover is September (Cloud cover 29).

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Average visibility in May
Decatur, IL

Average visibility in May - Decatur, IL
  • Average visibility in May: 6mi

Months with the highest visibility are January, February, March, April, May, June, September, October, November and December (6mi).
Months with the lowest visibility are July and August (5mi).

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