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 27°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 79°F (26°C) to 82°F (28°C). This is very warm water, allowing for extended stays without any discomfort. Swimming in these conditions will be particularly enjoyable, making it the ideal temperature range for those who want to relax in the sea. Additionally, water in this temperature range is suitable for children and elderly people, as it is comfortable for prolonged stays. 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 | 26.4°C | 26.0°C | |
| AUG 5 | 26.5°C | 26.0°C | |
| AUG 6 | 27.6°C | 26.0°C | |
| AUG 7 | 27.6°C | 26.0°C | |
| AUG 8 | 27.8°C | 26.0°C | |
| AUG 9 | 28.3°C | 26.0°C | |
| AUG 10 | 27.0°C | 26.0°C | |
| AUG 11 | 27.0°C | 26.0°C | |
| AUG 12 | 26.0°C | 27.0°C | |
| AUG 13 | 26.0°C | 26.9°C | |
| AUG 14 | 26.0°C | 26.9°C | |
| AUG 15 | 26.0°C | 26.8°C | |
| AUG 16 | 26.0°C | 26.8°C | |
| AUG 17 | 26.0°C | 26.7°C | |
| AUG 18 | 26.0°C | 26.7°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 | 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
August 12
August 13
August 14
August 15
August 16
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.