John W. Flannagan Reservoir — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in John W. Flannagan Reservoir, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in John W. Flannagan Reservoir 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 | 20.7°C | 24.0°C | |
| JUN 4 | 20.8°C | 24.0°C | |
| JUN 5 | 20.4°C | 24.0°C | |
| JUN 6 | 20.6°C | 24.0°C | |
| JUN 7 | 21.5°C | 24.0°C | |
| JUN 8 | 20.7°C | 24.0°C | |
| JUN 10 | 21.8°C | 24.0°C | |
| JUN 11 | 24.0°C | 21.9°C | |
| JUN 12 | 24.0°C | 22.0°C | |
| JUN 13 | 24.0°C | 22.1°C | |
| JUN 14 | 24.0°C | 22.2°C | |
| JUN 15 | 24.0°C | 22.4°C | |
| JUN 16 | 24.0°C | 22.5°C | |
| JUN 17 | 24.0°C | 22.6°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 | 10°C | 17°C |
| February | 3°C | 11°C | 19°C |
| March | 4°C | 12°C | 19°C |
| April | 11°C | 18°C | 25°C |
| May | 15°C | 21°C | 26°C |
| June | 20°C | 24°C | 27°C |
| July | 23°C | 28°C | 32°C |
| August | 22°C | 26°C | 30°C |
| September | 21°C | 26°C | 30°C |
| October | 15°C | 21°C | 26°C |
| November | 8°C | 16°C | 22°C |
| December | 4°C | 9°C | 13°C |
John W. Flannagan Reservoir: Water Temperature by Location
John W. Flannagan Reservoir: Weather Forecast
June 9
June 10
June 11
June 12
June 13
Location & Local Information
John W. Flannagan Reservoir, tucked into the mountains of southwestern Virginia, typically has cool water for much of the year. Surface temperatures in winter commonly sit around 33–45°F (1–7°C), with spring warming into roughly 40–60°F (4–16°C) as runoff and air temperatures rise. Peak summer temperatures often reach about 65–80°F (18–27°C) on warm days, although the reservoir’s depth and inflows keep deeper water substantially colder. In autumn the water generally cools back toward 50–65°F (10–18°C). Local weather, recent rainfall, and lake stratification can cause significant day-to-day and vertical variation in these values.
Swimming is not provided with staffed beaches at Flannagan and is generally considered at-your-own-risk rather than formally prohibited; the U.S. Army Corps of Engineers manages the site and emphasizes that there are no lifeguards. The combination of relatively cool temperatures even in summer, sudden drop-offs, submerged hazards, and boat traffic makes organized swimming limited and potentially hazardous. People who choose to enter the water are encouraged to be cautious, be aware of changing conditions, and use appropriate flotation, since safety services and marked swim areas are not a regular feature of the reservoir.