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 21.7°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 68°F (20°C) to 74°F (23°C). The water is warm and pleasant for swimming, and in this range, one can stay in the water for extended periods without the risk of hypothermia. This is the ideal temperature for relaxation, swimming, and water sports. Families with children, as well as outdoor enthusiasts, will enjoy swimming and time spent in the water. For most people, this is the optimal temperature for a comfortable beach experience. 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 |
|---|---|---|---|
| JUN 2 | 16.5°C | 18.7°C | |
| JUN 3 | 17.4°C | 18.7°C | |
| JUN 4 | 18.6°C | 18.7°C | |
| JUN 5 | 18.9°C | 18.7°C | |
| JUN 6 | 19.0°C | 18.7°C | |
| JUN 7 | 20.9°C | 18.7°C | |
| JUN 8 | 21.0°C | 18.7°C | |
| JUN 10 | 18.7°C | 21.6°C | |
| JUN 11 | 18.7°C | 21.4°C | |
| JUN 12 | 18.7°C | 21.3°C | |
| JUN 13 | 18.7°C | 21.1°C | |
| JUN 14 | 18.7°C | 21.0°C | |
| JUN 15 | 18.7°C | 20.8°C | |
| JUN 16 | 18.7°C | 20.7°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 | 22°C |
| July | 19°C | 24°C | 28°C |
| August | 22°C | 24°C | 27°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
June 9
June 10
June 11
June 12
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.