Climate and monthly weather forecastDeKalb, IL
Climate and monthly weather forecast
The climate of DeKalb
DeKalb, Illinois presents a Humid Continental climate with no dry season and a hot summer, marked by the Köppen climate classification 'Dfa'. Located in the Heartland of America, it receives year-round precipitation. The mercury moves dramatically from winter's cold to summer's warmth with the temperature fluctuating between 15.1°F (-9.4°C) in January and 80.2°F (26.8°C) in July. The relative humidity rate can regularly be seen at around 75% to 85%.A precipitation pattern exists in DeKalb, with approximately a maximum of 4.37" (111mm) occurring in May and a minimum of 1.65" (42mm) in February. Likewise, DeKalb equally experiences a variable rainfall day distribution, peaking at 18.3 days in May and dipping to 4.7 days in February. Snowfall, although uncommon, does make a seasonal appearance as well, with January observing around 5.55" (141mm) of snowfall over 11.8 days, and little to none recorded from May through September.
Visible fluctuations can be noticed with daylight, ranging from 9.2 hours in December up to 15.2 hours in June. Corresponding to the daylight, sunshine hours vary significantly from 3.6 hours in January to a summertime peak of 9.6 hours in July, with sunshine days experiencing slight fluctuations through the year. The UV index has its highest and lowest points in July and January respectively, aligning with the temperature trends.
Wind speeds in DeKalb are relatively stable, averaging around 9.9mph (15.9km/h) in January and February, and least in July with approximately 6.4mph (10.3km/h) being recorded. Gusts tend to mirror this with 15.6mph (25.1km/h) seen in January and slowing down to 10.4mph (16.7km/h) in July.
The best time to visit DeKalb
Undoubtedly, the best time to visit DeKalb lies in the months of May and June. With a relatively warm temperature high at around 68.7°F (20.4°C) to 77.7°F (25.4°C), a comfortable humidity at nearly 78-81%, and a delightful long daylight of about 14.6 to 15.2 hours, it certainly makes for an inviting weather. Furthermore, regular rain showers with a high of 4.37" (111mm) of rain in May are likely to keep the city verdant and blooming.The worst time to visit DeKalb
Conversely, the months of January and February are generally considered the least favorable time to explore DeKalb due to harsh winter conditions. With temperature lows of 15.1°F (-9.4°C), abruptly high snowfall levels of around 5.55" (141mm) in January, and a mere 9.5 to 10.6 hours of daylight, outdoor activities might be limited.Spring weather in DeKalb
In DeKalb, springtime witnesses a careful shift from the cold to a cooler and comfortable environment. The months from March to May record moderate temperature hikes between 30.2°F (-1°C) to 68.7°F (20.4°C), attributed to the gradual increase in daylight from 12 hours to 14.6 hours. Rainfall is a prominent feature, with April noting approximately 3.86" (98mm) of rainfall over 16.4 days, making spring a wet season.Summer weather in DeKalb
Summers in DeKalb, lasting from June until August, rise to a higher temperature level and extend up to 80.2°F (26.8°C). The city experiences its peak daylight during this season extending to around 15.2 hours in June. Coupled with promising sunshine of about 9.5 hours in June and July, summer inadvertently becomes an ideal timeframe for festivals and outdoor activities.Autumn weather in DeKalb
Fall in DeKalb, spanning from September to November, sees temperatures drop to a range of 54.5°F (12.5°C) to 73°F (22.8°C). Correspondingly, daylight hours decrease from 12.5 hours in September to 9.8 hours in November. The rainfall parameters drop to approximately 2.24" (57mm) in September but rise slightly to 2.68" (68mm) in October.Winter weather in DeKalb
Winter in DeKalb witnesses a stark drop in temperatures, falling to lows of around 15.1°F (-9.4°C) in January. Snowfall materializes predominantly in January with around 5.55" (141mm), dwindling down to minor amounts of about 2.91" (74mm) in February. With the shortest daylight duration observed in December at 9.2 hours, the visible sunshine reduces to about 3.9 hours in December.Weather in January
January weather in DeKalb, Illinois, is characterized by the chilling cold, with snowfall reaching a significant 5.55" (141mm). Typically, the town experiences its seasonal winter, inducing substantial cloud coverage. The short daylight hours compound the prevailing frostiness; people can sense nature's winter hibernation, the decreased daylight hours lending an icy white color palette to the landscape. Weather in January »Weather in February
The meteorological patterns of February maintain the winter's cold grip on DeKalb. This city sees a slight increase in temperature highs and lows, contrasted by a notable decrease in snowfall from 5.55" (141mm) to 3.86" (98mm). Weather in February »Weather in March
March marks the advent of spring in DeKalb, Illinois, with temperatures gradually inching upwards. A notable weather pattern during this transition period is an increase in rainfall from 1.65" (42mm) to 2.05" (52mm), replacing the substantial decrease in snowfall. Weather in March »Weather in April
April in DeKalb, Illinois, is characterized by a distinct shift towards pleasant, spring weather. There is a striking surge in rainfall from 2.05" (52mm) to 3.86" (98mm), emphasizing the change of seasons. The greenery starts to spread its reach, with budding trees and blooming flowers decorating the town. Weather in April »Weather in May
May is the harbinger of summer in DeKalb, and the pleasant weather makes it an appealing time for outdoor activities. Distinct from the preceding month, May sees the maximum rainfall of 4.37" (111mm) throughout the year. As the rainfall nourishes the abundant greenery, the increase in daylight hours adds to the lively atmosphere. Weather in May »Weather in June
DeKalb, Illinois, takes on a summery disposition in June. The month is characterized by the highest UV index of 6, matched with an upswing in temperature and humidity. June also brings about the longest daylight hours of the year, extending outdoor activities till late evening. Weather in June »Weather in July
July is usually the hottest month in DeKalb, with temperatures reaching an annual high of up to 80.2°F (26.8°C). While the warmth predominates, the frequent rain showers offer balmy respite. The landscape is adorned with full-grown plants, offering a plethora of shades of green to admire. Weather in July »Weather in August
In August, weather in DeKalb, Illinois slightly cools down from the peak summer heat. There is a marginal decrease in both temperature extremes, paired with slightly less precipitation compared to July. The town enjoys sunny episodes, punctuated by occasional showers that lend a fresh breath to the surroundings. Weather in August »Weather in September
September welcomes the fall season in DeKalb. A significant shift in the weather pattern can be seen, with temperature extremes experiencing a substantial drop without serious precipitation. The town undergoes a transformative phase, with leaves changing color and days getting steadily shorter. Weather in September »Weather in October
October in DeKalb, Illinois, heralds the full-fledged arrival of autumn. Along with regional fall traditions, this month sees an increase in rainfall, but without a drastic shift in temperature. Wind gusts take a leap from 7.2mph (11.6km/h) to 8.9mph (14.3km/h), whisking away the fallen leaves. Weather in October »Weather in November
The weather in November in DeKalb sets the stage for the nearing winter season. Snowfall sees a rise from 0.2" (5mm) to 1.81" (46mm), signifying the start of the colder months. As the temperature dips, people adjust to the shifting seasons and prepare for the wintry days ahead. Weather in November »Weather in December
December infuses the air of DeKalb, Illinois, with the crisp winter chill. The most significant change in this month's weather is the increase in snowfall from 1.81" (46mm) to 2.91" (74mm). Streets are often snow-covered, with festive decorations twinkling against the white background. Weather in December »Updated: Aug 5, 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
DeKalb's January weather, marked by an average high temperature of 27°F (-2.8°C) and an average low temperature of 15.1°F (-9.4°C), is the coldest in the year.
January and July, with an average relative humidity of 85%, are most humid months.
Throughout the year, there are 152.6 rainfall days, and 32.09" (815mm) of precipitation is accumulated.
January through May, October through December are months with snowfall in DeKalb.
The month with the most snowfall is January, when snow falls for 11.8 days and typically aggregates up to 5.55" (141mm) of snow.
Throughout the year, in DeKalb, Illinois, there are 44.3 snowfall days, and 17.87" (454mm) of snow is accumulated.
The month with the least sunshine is January, with an average of 3.6h of sunshine.
The months with the lowest UV index in DeKalb are January and December, with an average maximum UV index of 1.
The month with the least rainfall is February, when the rain falls for 4.7 days and typically collects 1.65" (42mm) of precipitation.
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.
April and October, with an average relative humidity of 75%, are the least humid months.
The month with the most rainfall is May, when the rain falls for 18.3 days and typically aggregates up to 4.37" (111mm) of precipitation.
June through September are months without snowfall.
June has the longest days of the year, with an average of 15h and 12min of daylight.
June and August, with an average maximum UV index of 6, are months with the highest UV index.
July is the warmest month of the year in DeKalb, registering average temperatures as high as 80.2°F (26.8°C) and as low as 63.1°F (17.3°C).
With an average of 9.6h of sunshine, July has the most sunshine of the year.
December has the shortest days of the year, with an average of 9h and 12min of daylight.
Average temperature
DeKalb, IL
The warmest month (with the highest average high temperature) is July (80.2°F).
The month with the lowest average high temperature is January (27°F).
The month with the highest average low temperature is July (63.1°F).
The coldest month (with the lowest average low temperature) is January (15.1°F).
Average pressure
DeKalb, IL
- Average pressure in January:
30.11"Hg - Average pressure in February:
30.1"Hg - Average pressure in March:
30.09"Hg - Average pressure in April:
29.95"Hg - Average pressure in May:
29.96"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:
30.03"Hg - Average pressure in October:
30"Hg - Average pressure in November:
30.09"Hg - Average pressure in December:
30.1"Hg
The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed
DeKalb, IL
- Average wind speed in January:
9.9mph - Average wind speed in February:
9.9mph - Average wind speed in March:
9.7mph - Average wind speed in April:
10mph - Average wind speed in May:
8.5mph - Average wind speed in June:
7.4mph
- Average wind speed in July:
6.4mph - Average wind speed in August:
6.2mph - Average wind speed in September:
7.2mph - Average wind speed in October:
8.9mph - Average wind speed in November:
9.6mph - Average wind speed in December:
9.3mph
The windiest month (with the highest average wind speed) is April (10mph).
The calmest month (with the lowest average wind speed) is August (6.2mph).
Average humidity
DeKalb, IL
The months with the highest relative humidity are January and July (85%).
The months with the lowest relative humidity are April and October (75%).
Average rainfall
DeKalb, IL
- Average rainfall in January:
1.81" - Average rainfall in February:
1.65" - Average rainfall in March:
2.05" - Average rainfall in April:
3.86" - Average rainfall in May:
4.37" - Average rainfall in June:
4.13"
- Average rainfall in July:
3.15" - Average rainfall in August:
2.72" - Average rainfall in September:
2.24" - Average rainfall in October:
2.68" - Average rainfall in November:
1.73" - Average rainfall in December:
1.69"
The wettest month (with the highest rainfall) is May (4.37").
The driest month (with the least rainfall) is February (1.65").
Average rainfall days
DeKalb, IL
- Average rainfall days in January:
5.7 days - Average rainfall days in February:
4.7 days - Average rainfall days in March:
12.2 days - Average rainfall days in April:
16.4 days - Average rainfall days in May:
18.3 days - Average rainfall days in June:
18.1 days
- Average rainfall days in July:
18.1 days - Average rainfall days in August:
15.8 days - Average rainfall days in September:
12.2 days - Average rainfall days in October:
13.1 days - Average rainfall days in November:
9.5 days - Average rainfall days in December:
8.5 days
The month with the highest number of rainy days is May (18.3 days).
The month with the least rainy days is February (4.7 days).
Average snowfall
DeKalb, IL
- Average snowfall in January:
5.55" - Average snowfall in February:
3.86" - Average snowfall in March:
2.17" - Average snowfall in April:
1.34" - Average snowfall in May:
0.04" - Average snowfall in June:
0"
The month with the highest snowfall is January (5.55").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days
DeKalb, IL
- Average snowfall days in January:
11.8 days - Average snowfall days in February:
10.6 days - Average snowfall days in March:
5.6 days - Average snowfall days in April:
1.7 days - Average snowfall days in May:
0.1 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:
0.8 days - Average snowfall days in November:
3.7 days - Average snowfall days in December:
10 days
The month with the highest number of snowfall days is January (11.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight / Average sunshine
DeKalb, IL
- Average daylight in January:
9h and 30min - Average daylight in February:
10h and 36min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 24min - Average daylight in May:
14h and 36min - Average daylight in June:
15h and 12min
- Average daylight in July:
14h and 54min - Average daylight in August:
13h and 48min - Average daylight in September:
12h and 30min - Average daylight in October:
11h and 6min - Average daylight in November:
9h and 48min - Average daylight in December:
9h and 12min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in January:
3h and 36min - Average sunshine in February:
3h and 48min - Average sunshine in March:
6h and 0min - Average sunshine in April:
7h and 24min - Average sunshine in May:
8h and 24min - Average sunshine in June:
9h and 30min
- Average sunshine in July:
9h and 36min - Average sunshine in August:
9h and 30min - Average sunshine in September:
8h and 30min - Average sunshine in October:
5h and 24min - Average sunshine in November:
5h and 0min - Average sunshine in December:
3h and 54min
The month with the most sunshine is July (Average sunshine: 9h and 36min).
The month with the least sunshine is January (Average sunshine: 3h and 36min).
Average sunshine days
DeKalb, IL
- Average sunshine days in January:
14.6 days - Average sunshine days in February:
13.4 days - Average sunshine days in March:
14.4 days - Average sunshine days in April:
10.8 days - Average sunshine days in May:
10.8 days - Average sunshine days in June:
10.3 days
- Average sunshine days in July:
10.3 days - Average sunshine days in August:
12.9 days - Average sunshine days in September:
15.7 days - Average sunshine days in October:
15.4 days - Average sunshine days in November:
17.2 days - Average sunshine days in December:
15.5 days
The month with the most sunshine days is November (17.2 days).
The months with the least sunshine days are June and July (10.3 days).
Average UV index
DeKalb, IL
The months with the highest UV index are June and August (UV index 6).
The months with the lowest UV index are January and December (UV index 1).
Average cloud cover
DeKalb, IL
The month with the most cloud cover is January (Cloud cover 63).
The months with the least cloud cover are August and September (Cloud cover 35).
Average visibility
DeKalb, IL
The months with the highest visibility are March, April, May, June, October, November and December (6mi).
The months with the lowest visibility are January, February, July, August and September (5mi).
