William H Harsha Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in William H Harsha Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in William H Harsha Lake today is 21.8°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 3 | 20.6°C | 21.7°C | |
| JUN 4 | 20.1°C | 21.7°C | |
| JUN 5 | 20.4°C | 21.7°C | |
| JUN 6 | 20.8°C | 21.7°C | |
| JUN 7 | 21.3°C | 21.7°C | |
| JUN 8 | 21.5°C | 21.7°C | |
| JUN 10 | 21.8°C | 21.7°C | |
| JUN 11 | 21.7°C | 21.8°C | |
| JUN 12 | 21.7°C | 21.8°C | |
| JUN 13 | 21.7°C | 21.8°C | |
| JUN 14 | 21.7°C | 21.8°C | |
| JUN 15 | 21.7°C | 21.8°C | |
| JUN 16 | 21.7°C | 21.8°C | |
| JUN 17 | 21.7°C | 21.8°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 | 3°C | 9°C | 14°C |
| February | 2°C | 9°C | 16°C |
| March | 2°C | 11°C | 19°C |
| April | 8°C | 14°C | 20°C |
| May | 14°C | 18°C | 22°C |
| June | 19°C | 22°C | 24°C |
| July | 18°C | 21°C | 24°C |
| August | 22°C | 24°C | 27°C |
| September | 21°C | 24°C | 26°C |
| October | 18°C | 21°C | 24°C |
| November | 8°C | 14°C | 19°C |
| December | 4°C | 9°C | 13°C |
William H Harsha Lake: Water Temperature by Location
William H Harsha Lake: Weather Forecast
June 9
June 10
June 11
June 12
June 13
Location & Local Information
William H. Harsha Lake in southwestern Ohio experiences wide seasonal variation in surface water temperature. In winter the lake hovers near freezing, roughly 33–40°F (1–4°C). Spring brings a gradual rise, typically 40–60°F (4–15°C) depending on air temperatures and runoff. By summer the surface commonly warms to about 68–80°F (20–27°C) at the peak of the season, though shallow coves can be a few degrees warmer on hot days. During autumn the water cools back into the 50–65°F (10–18°C) range as air temperatures decline. These are general ranges and actual readings vary day to day with weather, depth, and time of day.
Swimming at William H. Harsha Lake is generally allowed but is subject to management rules and seasonal openings of designated areas; many reservoirs permit swimming only in marked spots and do not provide lifeguards. Recreational use is balanced with boating, variable depths, sudden temperature changes, and occasional water-quality issues such as algal blooms, so officials may post advisories or close areas for safety. Visitors should check current advisories, use caution around boat traffic, and remember that colder or near-surface layers can produce strong thermal shock even on warm days, making cautious entry and awareness of conditions important.