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 25.3°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 75°F (23°C) to 79°F (26°C). This is a very comfortable temperature for swimming, and many people can enjoy prolonged stays in the water without feeling cold. The water is pleasantly warm, making it ideal for relaxation and water sports. This temperature range is particularly popular among tourists, as it combines comfort and safety for health. 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 23 | 25.9°C | 24.7°C | |
| JUN 24 | 25.8°C | 24.7°C | |
| JUN 25 | 25.8°C | 24.7°C | |
| JUN 26 | 25.6°C | 24.7°C | |
| JUN 27 | 25.5°C | 24.7°C | |
| JUN 28 | 25.1°C | 24.7°C | |
| JUN 29 | 25.2°C | 24.7°C | |
| JUN 30 | 25.3°C | 24.7°C | |
| JUL 1 | 27.8°C | 25.4°C | |
| JUL 2 | 27.8°C | 25.6°C | |
| JUL 3 | 27.8°C | 25.7°C | |
| JUL 4 | 27.8°C | 25.8°C | |
| JUL 5 | 27.8°C | 25.9°C | |
| JUL 6 | 27.8°C | 26.1°C | |
| JUL 7 | 27.8°C | 26.2°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
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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.