O'Neill Forebay Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in O'Neill Forebay Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in O'Neill Forebay Lake today is 27.9°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 24 | 29.4°C | 26.1°C | |
| AUG 25 | 29.4°C | 26.1°C | |
| AUG 26 | 29.2°C | 26.1°C | |
| AUG 27 | 28.5°C | 26.1°C | |
| AUG 28 | 28.2°C | 26.1°C | |
| AUG 29 | 28.2°C | 26.1°C | |
| AUG 30 | 27.9°C | 26.1°C | |
| AUG 31 | 27.9°C | 26.1°C | |
| SEP 1 | 23.0°C | 27.7°C | |
| SEP 2 | 23.0°C | 27.4°C | |
| SEP 3 | 23.0°C | 27.2°C | |
| SEP 4 | 23.0°C | 26.9°C | |
| SEP 5 | 23.0°C | 26.7°C | |
| SEP 6 | 23.0°C | 26.4°C | |
| SEP 7 | 23.0°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 | 9°C | 12°C | 14°C |
| February | 9°C | 11°C | 14°C |
| March | 6°C | 13°C | 21°C |
| April | 13°C | 17°C | 21°C |
| May | 14°C | 19°C | 25°C |
| June | 17°C | 22°C | 27°C |
| July | 18°C | 23°C | 29°C |
| August | 21°C | 26°C | 32°C |
| September | 19°C | 23°C | 27°C |
| October | 17°C | 21°C | 25°C |
| November | 13°C | 17°C | 21°C |
| December | 10°C | 14°C | 17°C |
O'Neill Forebay Lake: Water Temperature by Location
O'Neill Forebay Lake: Weather Forecast
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Location & Local Information
O'Neill Forebay, the smaller reservoir downstream of San Luis Reservoir in California’s Central Valley, tends to show pronounced seasonal variation in surface temperature. In winter the water commonly sits around 45–55°F (7–13°C), warming through spring to roughly 50–70°F (10–21°C). By summer, surface temperatures can reach about 65–80°F (18–27°C) on warm days, although deeper or shaded parts remain noticeably cooler. Autumn temperatures usually fall back into the 55–70°F (13–21°C) range. These are approximate surface values; the forebay’s depth, water releases and wind-driven mixing mean temperatures can change quickly and colder layers may be present beneath the surface.
Swimming at O'Neill Forebay is generally discouraged and in many locations effectively restricted because the area is used for water management, boating and fishing. Operational factors such as strong currents near intake structures and pumps, heavy boat traffic, submerged hazards and variable water quality create safety and health concerns. Cold water temperatures, especially in spring and winter, also raise the risk of cold shock. If someone is considering entering the water, they should confirm current local rules and advisories and take appropriate safety precautions.