Little Grassy Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Little Grassy Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Little Grassy Lake today is 29.5°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature is above 82°F (28°C). This is very warm water, which may feel almost hot to most people. Swimming in such conditions is perfect for those seeking relaxation and comfort in the water. These waters are often preferred for relaxation in hot weather, as the water temperature does not cool the body significantly. However, it is important to remember that in such warm waters, caution is necessary, as prolonged exposure without rest can lead to overheating. 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 | 27.2°C | 27.2°C | |
| AUG 5 | 27.3°C | 27.2°C | |
| AUG 6 | 28.5°C | 27.2°C | |
| AUG 7 | 28.9°C | 27.2°C | |
| AUG 8 | 28.9°C | 27.2°C | |
| AUG 9 | 29.1°C | 27.2°C | |
| AUG 10 | 29.2°C | 27.2°C | |
| AUG 11 | 29.4°C | 27.2°C | |
| AUG 12 | 27.2°C | 29.4°C | |
| AUG 13 | 27.2°C | 29.3°C | |
| AUG 14 | 27.2°C | 29.2°C | |
| AUG 15 | 27.2°C | 29.0°C | |
| AUG 16 | 27.2°C | 28.9°C | |
| AUG 17 | 27.2°C | 28.8°C | |
| AUG 18 | 27.2°C | 28.7°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 | 2°C | 4°C | 7°C |
| February | 2°C | 4°C | 7°C |
| March | 2°C | 7°C | 13°C |
| April | 8°C | 14°C | 20°C |
| May | 15°C | 19°C | 23°C |
| June | 20°C | 25°C | 29°C |
| July | 25°C | 28°C | 30°C |
| August | 25°C | 27°C | 30°C |
| September | 24°C | 27°C | 30°C |
| October | 17°C | 21°C | 24°C |
| November | 10°C | 14°C | 17°C |
| December | 4°C | 7°C | 10°C |
Little Grassy Lake: Water Temperature by Location
Little Grassy Lake: Weather Forecast
August 12
August 13
August 14
August 15
August 16
Location & Local Information
Little Grassy Lake in southern Illinois experiences a wide annual swing in surface water temperatures driven by seasonal air temperatures and lake depth. In spring (March–May) surface waters commonly range from about 40–60°F (4–16°C) as the lake thermally recovers from winter. Summer (June–August) brings the warmest conditions, with typical surface temperatures between roughly 70–85°F (21–29°C) on sunny, calm days; shallow bays can warm faster and occasionally exceed this. During fall (September–November) temperatures generally fall back to about 50–70°F (10–21°C) as cooling and turnover occur. In winter (December–February) the lake can approach freezing, often registering near 33–40°F (1–4°C) at the surface and developing ice in cold spells.
Swimming at Little Grassy Lake is possible in areas where local managers and signage permit it, but use is influenced by safety, watercraft traffic, and occasional water-quality considerations. There may be no lifeguards, and boat channels or marina zones are unsuitable for swimmers, so people should choose designated or clearly safe spots, heed posted rules, and be mindful that water as warm as mid‑70s°F (mid‑20s°C) is comfortable, while cooler temperatures increase risk of cold-water shock and fatigue.