Climate Insights for Harlan

Sioux County, Iowa, United States

Hottest
July
30°C peak
Coldest
January
-8°C low
Wettest
May
164mm rain
Best to Visit
July
Mild temps & low rain

Climate Overview

The climate in Harlan is temperate. The average annual temperature is 10°C and approximately 1001mm of precipitation falls per year. Harlan receives a notable amount of rainfall throughout the year, including during its driest month. Harlan is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: July, June, August. The coldest months are January, February, December, when temperatures can drop to -8°C. Snowfall occurs from January to December, with around 94cm accumulating over the season.

Temperature

-10° 10° 20° 30° Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Max: -1° Average: -5° Min: -8° Feb Max: 3° Average: -3° Min: -7° Mar Max: 10° Average: 4° Min: 0° Apr Max: 16° Average: 10° Min: 5° May Max: 22° Average: 16° Min: 12° Jun Max: 29° Average: 24° Min: 19° Jul Max: 30° Average: 25° Min: 20° Aug Max: 28° Average: 23° Min: 18° Sep Max: 26° Average: 20° Min: 15° Oct Max: 17° Average: 11° Min: 6° Nov Max: 10° Average: 4° Min: 0° Dec Max: 3° Average: -2° Min: -6°
Max
Average
Min

Harlan has a wide annual temperature range, spanning 38°C from the coldest to warmest months. The warmest month is July, when average highs reach 30°C and the mean temperature sits around 25°C. The coldest month is January, when overnight lows fall to -8°C and the daily average is -5°C. On average, daily temperatures fluctuate by about 10°C between overnight lows and afternoon highs. The sharpest temperature change occurs between September and October, with a 9°C shift in average temperatures.

Precipitation

0mm 50mm 100mm 150mm 200mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Precipitation: 33mm Snow: 21mm Feb Precipitation: 40mm Snow: 26mm Mar Precipitation: 79mm Snow: 10mm Apr Precipitation: 79mm Snow: 9mm May Precipitation: 164mm Snow: 0mm Jun Precipitation: 112mm Snow: 0mm Jul Precipitation: 78mm Snow: 0mm Aug Precipitation: 123mm Snow: 0mm Sep Precipitation: 108mm Snow: 0mm Oct Precipitation: 109mm Snow: 3mm Nov Precipitation: 35mm Snow: 7mm Dec Precipitation: 41mm Snow: 18mm
Precipitation
Snow

Harlan is a moderately rainy area, receiving approximately 1001mm of precipitation annually, which averages out to around 83mm per month. The wettest month is May, averaging 164mm of rainfall. August and June also tend to see above-average precipitation. The driest month is January, with just 33mm. That's 131mm less than May, the wettest month. Precipitation varies noticeably between seasons, with the first half (January to June) of the year generally seeing more rainfall. Snowfall is a regular feature from January to December, with around 94cm accumulating over the season. February typically sees the most snow at around 26cm.

Wind

0km/h 5km/h Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Wind Speed: 4km/h Feb Wind Speed: 5km/h Mar Wind Speed: 5km/h Apr Wind Speed: 5km/h May Wind Speed: 4km/h Jun Wind Speed: 4km/h Jul Wind Speed: 3km/h Aug Wind Speed: 3km/h Sep Wind Speed: 4km/h Oct Wind Speed: 5km/h Nov Wind Speed: 4km/h Dec Wind Speed: 4km/h
Wind Speed

Harlan is relatively calm, with an average annual wind speed of 4km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is April, averaging 5km/h, though still comfortable for most outdoor activities. The calmest conditions occur in July, with average winds dropping to 3km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 2km/h gap between the calmest and windiest months.

Seasons

Winter
Dec 21
Spring
Mar 20
Summer
Jun 21
Autumn
Sep 23

6 days until Summer

It is currently spring in Harlan, which began on March 20, 2026. Harlan is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in July at around 30°C, while the coldest stretch bottoms out in January near -8°C. Summer is next, beginning on June 21, 2026 — 6 days from now.

Spring

Temperatures range from 0 to 22°C. Rainfall is heavy, totalling around 322mm across the season with a monthly average of 107mm. Winds are generally light, averaging 5km/h. An umbrella or waterproof jacket is advisable as spring showers are frequent.

Summer

Temperatures range from 18 to 30°C. Rainfall is heavy, totalling around 313mm across the season with a monthly average of 104mm. Winds are generally light, averaging 4km/h. Light, breathable clothing is ideal — perfect conditions for outdoor activities.

Autumn

Temperatures range from 0 to 26°C. Precipitation is moderate at around 252mm for the season, averaging 84mm per month. Expect around 9cm of snow accumulation during this period. Winds are generally light, averaging 4km/h. A waterproof jacket and sturdy footwear are recommended as rain becomes more frequent.

Winter

Temperatures range from -8 to 3°C. Rainfall is relatively light, with around 114mm over the season and a monthly average of 38mm. Expect around 65cm of snow accumulation during this period. Winds are generally light, averaging 4km/h. Warm winter clothing and waterproof boots are a must, and travel may be affected by snow.

Best Time to Visit

Jan -5°
Feb -3°
Mar
Apr 10°
May 16°
Jun 24°
Jul 25°
Aug 23°
Sep 20°
Oct 11°
Nov
Dec -2°

The best time to visit Harlan is during July, when the weather is most comfortable for travellers. During these months, average temperatures hover around 25°C with modest rainfall averaging 78mm per month. By contrast, January can be quite cold with temperatures dropping to -8°C. Despite being the best months overall, some rain is still likely — pack a waterproof layer and plan a mix of indoor and outdoor activities.

Monthly Climate Data

The table below shows monthly climate averages for Harlan based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.

Month
Min Temperature
Max Temperature
Wind Speed
Precipitation
Snow
Jan
-8 °C
-1 °C
4 km/h
33 mm
21 cm
Feb
-7 °C
3 °C
5 km/h
40 mm
26 cm
Mar
0 °C
10 °C
5 km/h
79 mm
10 cm
Apr
5 °C
16 °C
5 km/h
79 mm
9 cm
May
12 °C
22 °C
4 km/h
164 mm
0 cm
Jun Current
19 °C
29 °C
4 km/h
112 mm
0 cm
Jul
20 °C
30 °C
3 km/h
78 mm
0 cm
Aug
18 °C
28 °C
3 km/h
123 mm
0 cm
Sep
15 °C
26 °C
4 km/h
108 mm
0 cm
Oct
6 °C
17 °C
5 km/h
109 mm
3 cm
Nov
0 °C
10 °C
4 km/h
35 mm
7 cm
Dec
-6 °C
3 °C
4 km/h
41 mm
18 cm
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