Climate Insights for Green Rock

Whatcom County, Illinois, United States

Hottest
July
30°C peak
Coldest
January
-7°C low
Wettest
May
128mm rain
Best to Visit
July, August
Mild temps & low rain

Climate Overview

The climate in Green Rock is temperate. The average annual temperature is 11°C and approximately 1064mm of precipitation falls per year. Green Rock receives a notable amount of rainfall throughout the year, including during its driest month. Green Rock 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 -7°C. Snowfall occurs from January to December, with around 92cm accumulating over the season.

Temperature

-10° 10° 20° 30° Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Max: 0° Average: -4° Min: -7° Feb Max: 4° Average: -1° Min: -5° Mar Max: 10° Average: 5° Min: 0° Apr Max: 16° Average: 10° Min: 5° May Max: 23° Average: 17° Min: 12° Jun Max: 29° Average: 23° Min: 18° 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: 12° Min: 8° Nov Max: 9° Average: 5° Min: 1° Dec Max: 3° Average: -1° Min: -4°
Max
Average
Min

Green Rock has a wide annual temperature range, spanning 37°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 -7°C and the daily average is -4°C. On average, daily temperatures fluctuate by about 9°C between overnight lows and afternoon highs. The sharpest temperature change occurs between September and October, with a 8°C shift in average temperatures.

Precipitation

0mm 25mm 50mm 75mm 100mm 125mm 150mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Precipitation: 53mm Snow: 22mm Feb Precipitation: 59mm Snow: 20mm Mar Precipitation: 93mm Snow: 12mm Apr Precipitation: 107mm Snow: 6mm May Precipitation: 128mm Snow: 0mm Jun Precipitation: 120mm Snow: 0mm Jul Precipitation: 83mm Snow: 0mm Aug Precipitation: 90mm Snow: 0mm Sep Precipitation: 117mm Snow: 0mm Oct Precipitation: 108mm Snow: 5mm Nov Precipitation: 55mm Snow: 12mm Dec Precipitation: 50mm Snow: 15mm
Precipitation
Snow

Green Rock is a moderately rainy area, receiving approximately 1064mm of precipitation annually, which averages out to around 89mm per month. The wettest month is May, averaging 128mm of rainfall. June and September also tend to see above-average precipitation. The driest month is December, with just 50mm. That's 78mm 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 92cm accumulating over the season. January typically sees the most snow at around 22cm.

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

Green Rock 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 March, averaging 4km/h, though still comfortable for most outdoor activities. The calmest conditions occur in August, 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 1km/h gap between the calmest and windiest months.

Seasons

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

7 days until Summer

It is currently spring in Green Rock, which began on March 20, 2026. Green Rock 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 -7°C. Summer is next, beginning on June 21, 2026 — 7 days from now.

Spring

Temperatures range from 0 to 23°C. Rainfall is heavy, totalling around 328mm across the season with a monthly average of 109mm. Winds are generally light, averaging 4km/h. An umbrella or waterproof jacket is advisable as spring showers are frequent.

Summer

Temperatures range from 18 to 30°C. Precipitation is moderate at around 293mm for the season, averaging 98mm per month. Winds are generally light, averaging 3km/h. Light, breathable clothing is ideal — perfect conditions for outdoor activities.

Autumn

Temperatures range from 1 to 26°C. Precipitation is moderate at around 280mm for the season, averaging 93mm per month. Expect around 17cm 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 -7 to 4°C. Precipitation is moderate at around 162mm for the season, averaging 54mm per month. Expect around 57cm 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 -4°
Feb -1°
Mar
Apr 10°
May 17°
Jun 23°
Jul 25°
Aug 23°
Sep 20°
Oct 12°
Nov
Dec -1°

The best time to visit Green Rock is during July and August, when the weather is most comfortable for travellers. During these months, average temperatures hover around 24°C with modest rainfall averaging 86mm per month. By contrast, January can be quite cold with temperatures dropping to -7°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 Green Rock 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
-7 °C
0 °C
4 km/h
53 mm
22 cm
Feb
-5 °C
4 °C
4 km/h
59 mm
20 cm
Mar
0 °C
10 °C
4 km/h
93 mm
12 cm
Apr
5 °C
16 °C
4 km/h
107 mm
6 cm
May
12 °C
23 °C
4 km/h
128 mm
0 cm
Jun Current
18 °C
29 °C
3 km/h
120 mm
0 cm
Jul
20 °C
30 °C
3 km/h
83 mm
0 cm
Aug
18 °C
28 °C
3 km/h
90 mm
0 cm
Sep
15 °C
26 °C
3 km/h
117 mm
0 cm
Oct
8 °C
17 °C
4 km/h
108 mm
5 cm
Nov
1 °C
9 °C
4 km/h
55 mm
12 cm
Dec
-4 °C
3 °C
4 km/h
50 mm
15 cm
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