Grass Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Grass Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Grass Lake today is 27.7°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 79°F (26°C) to 82°F (28°C). This is very warm water, allowing for extended stays without any discomfort. Swimming in these conditions will be particularly enjoyable, making it the ideal temperature range for those who want to relax in the sea. Additionally, water in this temperature range is suitable for children and elderly people, as it is comfortable for prolonged stays. It is important to note that these swimming tips and recommendations apply only in good weather. When the air temperature is below 68°F (20°C), and sometimes even below 77°F (25°C), swimming can be unpleasant even with relatively high water temperatures.
Water Temperature Chart Over the Last 30 Days
Table of Daily Sea Temperature Data
| Date | Current | Average | Forecast |
|---|---|---|---|
| AUG 4 | 26.0°C | 24.8°C | |
| AUG 5 | 26.3°C | 24.8°C | |
| AUG 6 | 26.4°C | 24.8°C | |
| AUG 7 | 27.5°C | 24.8°C | |
| AUG 8 | 27.6°C | 24.8°C | |
| AUG 9 | 27.7°C | 24.8°C | |
| AUG 10 | 27.7°C | 24.8°C | |
| AUG 11 | 27.7°C | 24.8°C | |
| AUG 12 | 24.8°C | 27.6°C | |
| AUG 13 | 24.8°C | 27.4°C | |
| AUG 14 | 24.8°C | 27.3°C | |
| AUG 15 | 24.8°C | 27.1°C | |
| AUG 16 | 24.8°C | 27.0°C | |
| AUG 17 | 24.8°C | 26.8°C | |
| AUG 18 | 24.8°C | 26.7°C |
* Current - Actual water temperature value
** Average - Average water temperature on this day in recent years
*** Forecast - Our water temperature forecast
Actual nearshore water temperatures may fluctuate by several degrees from the reported values, especially following heavy rainfall or extended periods of strong winds. Certain wind patterns can cause colder, deeper waters to rise and replace the sun-warmed surface water, leading to noticeable variations.
Our forecast is based on a proprietary mathematical model that considers real-time water temperature changes, historical trends, key weather patterns, wind strength and direction, and air temperature specific to each region. Additionally, we incorporate data from other resorts to enhance accuracy.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 0°C | 3°C | 7°C |
| February | 1°C | 4°C | 7°C |
| March | 2°C | 5°C | 8°C |
| April | 5°C | 9°C | 13°C |
| May | 10°C | 14°C | 19°C |
| June | 16°C | 19°C | 23°C |
| July | 19°C | 24°C | 30°C |
| August | 22°C | 25°C | 28°C |
| September | 18°C | 21°C | 23°C |
| October | 11°C | 15°C | 19°C |
| November | 0°C | 7°C | 13°C |
| December | 3°C | 3°C | 8°C |
Grass Lake: Water Temperature by Location
Grass Lake: Weather Forecast
August 12
August 13
August 14
August 15
Location & Local Information
Grass Lake in Illinois experiences the same seasonal swings in water temperature typical of shallow Midwestern lakes. In winter the surface can hover near freezing, roughly 32–39°F (0–4°C), often colder beneath the ice when present. As spring warms, the water commonly rises into the 40s and 50s Fahrenheit, about 4–15°C, before summer brings the highest surface readings in the mid-60s to upper 70s °F, approximately 18–26°C; during heat waves shallow areas can reach the low 80s °F (27–28°C). In autumn the lake cools again, moving through roughly 50–65°F (10–18°C) as turnover and shorter days lower temperatures. These ranges are general and will vary with depth, shading, and recent weather.
Swimming is generally possible at Grass Lake when public access and local rules permit, particularly during the warmer months when surface temperatures are comfortable for recreation. Whether swimming is allowed depends on ownership, posted regulations, and water quality; authorities may close areas or post advisories for harmful algal blooms, bacterial contamination, or unsafe conditions such as submerged hazards or lack of lifeguards. For safety, swimmers should follow signage, avoid areas with visible algal scums, and be mindful that even warm surface temperatures can conceal cold pockets or sudden depth changes.