Climate and monthly weather forecastHarrisburg, IL
Climate and monthly weather forecast
The climate of Harrisburg
Harrisburg, nestled in Illinois, USA, falls under the Cfa category of the Köppen climate classification which translates to a humid subtropical climate with no dry season. This location is unequivocally subjected to intricate weather patterns throughout the year, affected by a harmonious blend of diverse climatic parameters.A striking feature of the climate here is the consistent fluctuation in weather conditions. The annual temperature swing ranges from an average low of 26.2°F (-3.2°C) in January to a high of - 87.3°F (30.7°C) in July, while humidity levels stay reasonably stable, averaging in the mid 70s percentile. Even rainfall does not deviate greatly, averaging 3.71" (94mm) per month, though peaking at 4.8" (122mm) in April.
Intriguingly, snowfall is minimal, predominantly featuring during the winter period, and disappears completely from May to September. Daylight hours see a predictable increase as the year progresses, reaching their zenith in June with 14.7 hours, before receding again. The recorded UV index is highest in the summer months, reflecting the overall sunnier conditions, while wind speeds exhibit negligible variance, on average veering around the 8mph (12.9km/h) mark.
Unique weather patterns become notably perceived when observing certain months. July and August host the highest temperatures coupled with an elevated UV index. Conversely, December and January offer the coolest conditions, interspersed with snowfall.
The best time to visit Harrisburg
The most favorable period for a planned visit to Harrisburg lies between May and September. This time of the year is characterized by pleasantly warm temperatures which typically range from 66.4°F (19.1°C) to 85.6°F (29.8°C), perfect for outdoor activities. The summer months also offer the longest daylight hours, peaking at 14.7 hours in June, granting copious time to explore and appreciate the beauty of Harrisburg.The worst time to visit Harrisburg
On the polar end of the spectrum, the span from December to February generally proves to be less suitable for tourists. This stretch is dominated by lower temperatures, often dipping to a chilling 26.2°F (-3.2°C) in January. Accompanied by snowfall, this period can be especially inconvenient for visitors unaccustomed to cold weather conditions.Spring weather in Harrisburg
March to May form the spring season in Harrisburg, characterized by a marked rise in temperatures from 55°F (12.8°C) in March to 75.6°F (24.2°C) in May. Rainfall also sees an uptick during these months, with an apex of 4.8" (122mm) being recorded in April. Daylight routines align with this shift, lengthening progressively to reach an average of 14.2 hours per day by May.Summer weather in Harrisburg
The sultry summer season in Harrisburg, spanning from June to August, is typified by warm conditions. Ambient temperatures generally fluctuate between 80.8°F (27.1°C) and 85.6°F (29.8°C), with the UV index attaining its zenith during these months. Remarkably, despite the balmy climate, rainfall gently reduces across these months to attain an average of 2.52" (64mm) in August.Autumn weather in Harrisburg
Autumn graces Harrisburg between September and November, ushering in tranquil weather. Conditions slightly cool down from 80.8°F (27.1°C) in September to 53.8°F (12.1°C) in November, which marries well with the diminishing daylight hours and the gradual decrease in humidity. Rainfall sees a resurgence during the latter part of this season, reaching 2.64" (67mm) in November.Winter weather in Harrisburg
Winter in Harrisburg embraces the months from December to February. These months witness a distinctive drop in temperatures, plunging to the lowest annual average of 26.2°F (-3.2°C) in January. With shrinking daylight, Harrisburg brings forward copious chances of snowfall, registering 1.73" (44mm) in December and 1.65" (42mm) in February. This period also strikingly reveals lower cloud cover, enabling clearer skies.Weather in January
January features the coldest temperatures amidst the year in Harrisburg, Illinois with temperatures fluctuating from 26.2°F (-3.2°C) to 39.7°F (4.3°C). As one could expect, this is the beginning of the Winter season, boasting a wintry tableau of frosty mornings and chilly nights. Weather in January »Weather in February
Progressing from January to February, the weather in Harrisburg, Illinois sees a minor uptick, featuring temperatures from 30.2°F (-1°C) to 44.1°F (6.7°C). Amidst the overall cool ambiance, one can expect to witness an increase in daylight hours, on the one hand allowing more sunshine and on the other hand rendering February somewhat warmer than its predecessor. Weather in February »Weather in March
With the arrival of March begins the transition from Winter to Spring in Harrisburg, Illinois. The city experiences an apparent increase in temperatures, as they range from 39.2°F (4°C) to 55°F (12.8°C). March stands out as a month of changing weather patterns, with the cold giving way to comparatively warmer days. Weather in March »Weather in April
April in Harrisburg, Illinois promises the full blush of Spring, with a significant rise in temperatures from 48.7°F (9.3°C) to 66.4°F (19.1°C). Spring blooms find their peak this month, offering a delightful show of colors and fragrances all through the city. Weather in April »Weather in May
The weather in May introduces the early signs of Summer in Harrisburg, Illinois. Temperature variance is noticeable throughout May, ranging from 58.1°F (14.5°C) to 75.6°F (24.2°C). This month typically grants a balance of weather conditions, with comfortable, warm days set against relatively cooler nights. Weather in May »Weather in June
June marks the commencement of the Summer season in Harrisburg, Illinois. Temperatures maintain within the limits of 66.2°F (19°C) to 84.7°F (29.3°C), giving inhabitants a taste of intense warmth. Typically characterized by sunny days and balmy nights, June provides an ideal setting for numerous outdoor activities, including barbecuing and poolside lounging. Weather in June »Weather in July
In Harrisburg, Illinois, July stands out as the warmest month, with temperatures soaring from 68.5°F (20.3°C) up to 87.3°F (30.7°C). The city epitomizes the height of Summer during this phase, with several sunny, hot days. Considering the substantial rise in temperatures, locals and visitors alike are drawn towards water-based activities for respite from the heat. Weather in July »Weather in August
August in Harrisburg, Illinois witnesses the grandeur of a typical late summer. Temperatures remain comparably high, ranging from 66°F (18.9°C) to 85.6°F (29.8°C), albeit a slight dip from July. The hot and sunny weather forms the perfect backdrop for enjoying summer festivities and water sports, although the scorching sun might call for necessary precautions. Weather in August »Weather in September
September in Harrisburg, Illinois marks the transition from Summer to Autumn, with temperatures fluctuating between 60.4°F (15.8°C) and 80.8°F (27.1°C). A noticeable relief from the high summer temperatures, September brings along cooler days and nights. Weather in September »Weather in October
September’s chill extends into October in Harrisburg, Illinois, resulting in a further dip in temperatures, from 49.3°F (9.6°C) to 67.8°F (19.9°C). This month is an integral part of the Fall season, which brings along diverse hues of orange, gold, and red to the leafy landscape. Weather in October »Weather in November
November brings the depth of Fall to a close, paving the way for the opening scenes of Winter in Harrisburg, Illinois. Temperature readings show a substantial drop from the previous months with a range from 38.7°F (3.7°C) to 53.8°F (12.1°C). Weather in November »Weather in December
In December, Harrisburg, Illinois plunges into the heart of Winter. Temperatures during this month vary from 32.4°F (0.2°C) to 44.1°F (6.7°C), bringing back the characteristic chill of the Winter season. The likelihood of snowfall increases towards the end of the month, painting the cityscape white. Weather in December »Updated: Jul 21, 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
January, characterized by an average high temperature of 39.7°F (4.3°C) and a low temperature of 26.2°F (-3.2°C), is generally the coldest month in Harrisburg.
Throughout the year, there are 158.6 rainfall days, and 36.02" (915mm) of precipitation is accumulated.
Months with snowfall are January through April, October through December.
January is the month with the most snowfall. Snow falls for 5.3 days and accumulates 1.73" (44mm) of snow.
In Harrisburg, during the entire year, snow falls for 17.7 days and aggregates up to 6.57" (167mm) of snow.
January has the least sunshine of the year, with an average of 4.6h of sunshine.
The months with the lowest UV index are January, February and December, with an average maximum UV index of 2.
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts in Harrisburg, 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 is the month with the most rainfall. Rain falls for 16.6 days and accumulates 4.8" (122mm) of precipitation.
With an average relative humidity of 79%, May is the most humid month.
In Harrisburg, snow does not fall in May through September.
The months with the highest UV index are May through August, with an average maximum UV index of 6.
June has the longest days of the year, with an average of 14h and 42min of daylight.
June has the most sunshine of the year, with an average of 10.6h of sunshine.
The warmest temperatures occur during July, when averages reach a peak of 87.3°F (30.7°C) and a low of 68.5°F (20.3°C).
The month with the least rainfall is September, when the rain falls for 10.5 days and typically collects 1.57" (40mm) of precipitation.
The least humid month is October, with an average relative humidity of 70%.
December has the shortest days of the year, with an average of 9h and 36min of daylight.
Average temperature
Harrisburg, IL
The warmest month (with the highest average high temperature) is July (87.3°F).
The month with the lowest average high temperature is January (39.7°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 (26.2°F).
Average pressure
Harrisburg, IL
- Average pressure in January:
30.16"Hg - Average pressure in February:
30.12"Hg - Average pressure in March:
30.08"Hg - Average pressure in April:
29.96"Hg - Average pressure in May:
29.97"Hg - Average pressure in June:
29.94"Hg
- Average pressure in July:
29.98"Hg - Average pressure in August:
29.98"Hg - Average pressure in September:
30.03"Hg - Average pressure in October:
30.04"Hg - Average pressure in November:
30.14"Hg - Average pressure in December:
30.14"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).
Average wind speed
Harrisburg, IL
- Average wind speed in January:
9.4mph - Average wind speed in February:
9.4mph - Average wind speed in March:
9.3mph - Average wind speed in April:
9.3mph - Average wind speed in May:
7.8mph - Average wind speed in June:
6.6mph
- Average wind speed in July:
5.8mph - Average wind speed in August:
5.8mph - Average wind speed in September:
6.4mph - Average wind speed in October:
8mph - Average wind speed in November:
8.5mph - Average wind speed in December:
8.8mph
The windiest months (with the highest average wind speed) are January and February (9.4mph).
The calmest months (with the lowest average wind speed) are July and August (5.8mph).
Average humidity
Harrisburg, IL
The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (70%).
Average rainfall
Harrisburg, IL
- Average rainfall in January:
2.68" - Average rainfall in February:
2.8" - Average rainfall in March:
3.39" - Average rainfall in April:
4.8" - Average rainfall in May:
3.86" - Average rainfall in June:
3.46"
- Average rainfall in July:
2.87" - Average rainfall in August:
2.52" - Average rainfall in September:
1.57" - Average rainfall in October:
2.64" - Average rainfall in November:
2.64" - Average rainfall in December:
2.8"
The wettest month (with the highest rainfall) is April (4.8").
The driest month (with the least rainfall) is September (1.57").
Average rainfall days
Harrisburg, IL
- Average rainfall days in January:
9.8 days - Average rainfall days in February:
10.8 days - Average rainfall days in March:
15.4 days - Average rainfall days in April:
16.6 days - Average rainfall days in May:
18.5 days - Average rainfall days in June:
15.6 days
- Average rainfall days in July:
17.1 days - Average rainfall days in August:
13.8 days - Average rainfall days in September:
10.5 days - Average rainfall days in October:
10.5 days - Average rainfall days in November:
9.7 days - Average rainfall days in December:
10.3 days
The month with the highest number of rainy days is May (18.5 days).
The month with the least rainy days is November (9.7 days).
Average snowfall
Harrisburg, IL
The month with the highest snowfall is January (1.73").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days
Harrisburg, IL
- Average snowfall days in January:
5.3 days - Average snowfall days in February:
5.1 days - Average snowfall days in March:
1.8 days - Average snowfall days in April:
0.6 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:
1.2 days - Average snowfall days in December:
3.6 days
The month with the highest number of snowfall days is January (5.3 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight / Average sunshine
Harrisburg, IL
- Average daylight in January:
9h and 54min - Average daylight in February:
10h and 48min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 12min - Average daylight in May:
14h and 12min - Average daylight in June:
14h and 42min
- Average daylight in July:
14h and 30min - Average daylight in August:
13h and 36min - Average daylight in September:
12h and 24min - Average daylight in October:
11h and 12min - Average daylight in November:
10h and 6min - Average daylight in December:
9h and 36min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in January:
4h and 36min - Average sunshine in February:
4h and 42min - Average sunshine in March:
6h and 18min - Average sunshine in April:
8h and 36min - Average sunshine in May:
9h and 12min - Average sunshine in June:
10h and 36min
- Average sunshine in July:
10h and 30min - Average sunshine in August:
10h and 18min - Average sunshine in September:
9h and 12min - Average sunshine in October:
6h and 42min - Average sunshine in November:
5h and 36min - Average sunshine in December:
4h and 42min
The month with the most sunshine is June (Average sunshine: 10h and 36min).
The month with the least sunshine is January (Average sunshine: 4h and 36min).
Average sunshine days
Harrisburg, IL
- Average sunshine days in January:
16.2 days - Average sunshine days in February:
13.1 days - Average sunshine days in March:
12.6 days - Average sunshine days in April:
11.5 days - Average sunshine days in May:
9.9 days - Average sunshine days in June:
12.1 days
- Average sunshine days in July:
12.2 days - Average sunshine days in August:
15 days - Average sunshine days in September:
17.1 days - Average sunshine days in October:
19.5 days - Average sunshine days in November:
17.7 days - Average sunshine days in December:
16.9 days
The month with the most sunshine days is October (19.5 days).
The month with the least sunshine days is May (9.9 days).
Average UV index
Harrisburg, IL
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 and December (UV index 2).
Average cloud cover
Harrisburg, IL
The months with the most cloud cover are January and February (Cloud cover 51).
The months with the least cloud cover are June and September (Cloud cover 28).
Average visibility
Harrisburg, 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).
