Decatur
Illinois, USA
Long-term weather forecast
Long-term weather forecast

Monthly weather forecast and climate
Decatur, IL

January, the same as December, is a wintry winter month in Decatur, Illinois, with average temperature ranging between max 33.8°F (1°C) and min 15.8°F (-9°C). With an average high-temperature of 33.8°F (1°C) and an average low-temperature of 15.8°F (-9°C), January is the coldest month. Weather in January »
February, the last month of the winter, in Decatur, is also a wintry month, with average temperature fluctuating between 39.2°F (4°C) and 19.4°F (-7°C). In February, the average high-temperature marginally rises, from a wintry 33.8°F (1°C) in January, to a still cold 39.2°F (4°C). Weather in February »

March, the first month of the spring, in Decatur, is a fresh month, with average temperature fluctuating between 30.2°F (-1°C) and 51.8°F (11°C). In March, the average high-temperature increases, from a wintry 39.2°F (4°C) in February, to a cool 51.8°F (11°C). Weather in March »

April is an enjoyable spring month in Decatur, Illinois, with average temperature fluctuating between 64.4°F (18°C) and 41°F (5°C). In Decatur, the average high-temperature in April rises, from a cool 51.8°F (11°C) in March, to an enjoyable 64.4°F (18°C). Weather in April »

May, the last month of the spring, in Decatur, is a warm month, with temperature in the range of an average high of 75.2°F (24°C) and an average low of 51.8°F (11°C). In Decatur, Illinois, the average high-temperature in May rises, from a comfortable 64.4°F (18°C) in April, to a moderately hot 75.2°F (24°C). Weather in May »

The first month of the summer, June, is still a warm month in Decatur, Illinois, with average temperature ranging between max 84.2°F (29°C) and min 60.8°F (16°C). In Decatur, the average high-temperature rises, from a moderately hot 75.2°F (24°C) in May, to a still warm 84.2°F (29°C). Weather in June »

July is a hot summer month in Decatur, Illinois, with temperature in the range of an average high of 87.8°F (31°C) and an average low of 64.4°F (18°C). July is the warmest month, with an average high-temperature of 87.8°F (31°C) and an average low-temperature of 64.4°F (18°C). Weather in July »

The last month of the summer, August, is also a moderately hot month in Decatur, Illinois, with temperature in the range of an average high of 84.2°F (29°C) and an average low of 62.6°F (17°C). In Decatur, the average high-temperature in August is practically the same as in July - a moderately hot 84.2°F (29°C). Weather in August »

The first month of the autumn, September, is also a moderately hot month in Decatur, Illinois, with temperature in the range of an average high of 78.8°F (26°C) and an average low of 55.4°F (13°C). In September, the average high-temperature marginally drops, from 84.2°F (29°C) in August, to a still moderately hot 78.8°F (26°C). Weather in September »

October, the same as September, in Decatur, Illinois, is an agreeable autumn month, with average temperature varying between 42.8°F (6°C) and 68°F (20°C). In October, the average high-temperature decreases, from a moderately hot 78.8°F (26°C) in September, to a pleasant 68°F (20°C). Weather in October »

The last month of the autumn, November, is also a fresh month in Decatur, Illinois, with average temperature fluctuating between 33.8°F (1°C) and 51.8°F (11°C). In Decatur, the average high-temperature significantly decreases, from an agreeable 68°F (20°C) in October, to a fresh 51.8°F (11°C). Weather in November »

The first month of the winter, December, is still a cold month in Decatur, Illinois, with average temperature ranging between max 37.4°F (3°C) and min 21.2°F (-6°C). In December, the average high-temperature significantly decreases, from a fresh 51.8°F (11°C) in November, to a cold 37.4°F (3°C). Weather in December »

What is the coldest month in Decatur?

January is the coldest month in Decatur, with an average high-temperature of 33.8°F (1°C) and an average low-temperature of 15.8°F (-9°C).

How much does it rain in Decatur?

In Decatur, during the entire year, the rain falls for 116 days and collects up to 38.4" (975mm) of precipitation.

What is the month with the lowest UV index in Decatur?

January, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Decatur.

What is the driest month in Decatur?

February is the month with the least rainfall. Rain falls for 9 days and accumulates 1.9" (48mm) of precipitation.

When are the longest days in Decatur?

June has the longest days of the year, with an average of 15h of daylight.

What is the month with the most sunshine in Decatur?

Months with the most sunshine are June and July, with an average of 10h of sunshine.

What is the month with the highest UV index in Decatur?

Months with the highest UV index in Decatur, Illinois, are June and July, with an average maximum UV index of 9.

What is the warmest month in Decatur?

The warmest month is July, with an average high-temperature of 87.8°F (31°C) and an average low-temperature of 64.4°F (18°C).

What is the wettest month in Decatur?

July is the month with the most rainfall. Rain falls for 9 days and accumulates 4.2" (107mm) of precipitation.

What is the month with the least sunshine in Decatur?

Months with the least sunshine in Decatur, Illinois, are November and December, with an average of 4h of sunshine.

What is the month with the shortest days in Decatur?

December has the shortest days of the year in Decatur, with an average of 9.4h of daylight.
Average rainfall - Decatur, IL
Average rainfall days - Decatur, IL

Months with the highest number of rainy days are March and April (12 days).
Months with the lowest number of rainy days are August, September and October (8 days).

Average daylight / Average sunshine - Decatur, IL