Union Valley Reservoir — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Union Valley Reservoir, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Union Valley Reservoir today is 18.8°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
⚠️ As of today, the minimum water temperature ranges from 65°F (18°C) to 68°F (20°C). This is already quite warm water, which is ideal for most people. Swimming becomes comfortable, and prolonged stays in the water do not cause discomfort. This temperature is perfect for family trips and for those who prefer warmer water. It is also comfortable for water sports such as surfing or swimming. 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 | 16.6°C | 16.0°C | |
| JUN 24 | 19.8°C | 16.0°C | |
| JUN 25 | 19.6°C | 16.0°C | |
| JUN 26 | 19.6°C | 16.0°C | |
| JUN 27 | 19.4°C | 16.0°C | |
| JUN 28 | 19.4°C | 16.0°C | |
| JUN 29 | 18.3°C | 16.0°C | |
| JUN 30 | 18.9°C | 16.0°C | |
| JUL 1 | 21.5°C | 18.9°C | |
| JUL 2 | 21.5°C | 19.1°C | |
| JUL 3 | 21.5°C | 19.2°C | |
| JUL 4 | 21.5°C | 19.3°C | |
| JUL 5 | 21.5°C | 19.5°C | |
| JUL 6 | 21.5°C | 19.6°C | |
| JUL 7 | 21.5°C | 19.7°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 | 4°C | 6°C | 9°C |
| February | 3°C | 5°C | 7°C |
| March | 3°C | 7°C | 11°C |
| April | 5°C | 9°C | 12°C |
| May | 7°C | 12°C | 17°C |
| June | 10°C | 16°C | 22°C |
| July | 16°C | 22°C | 27°C |
| August | 20°C | 24°C | 27°C |
| September | 19°C | 23°C | 26°C |
| October | 12°C | 16°C | 20°C |
| November | 7°C | 12°C | 16°C |
| December | 5°C | 8°C | 10°C |
Union Valley Reservoir: Water Temperature by Location
Union Valley Reservoir: Weather Forecast
July 1
July 2
July 3
July 4
Location & Local Information
Union Valley Reservoir, a high‑elevation lake in the Sierra Nevada, stays relatively cold most of the year. Typical surface temperatures in winter hover near freezing, roughly 34–40°F (1–4°C). Spring and early summer bring gradual warming to about 45–60°F (7–15°C) as snowmelt feeds the lake. Peak summer conditions can push surface readings into the mid‑50s to upper‑60s°F (13–20°C) on warm, calm afternoons, though deeper water remains much colder. In autumn the lake cools again, commonly ranging from about 40–55°F (4–13°C) depending on weather. These are approximate seasonal bands; actual temperatures vary with elevation, depth, inflow, and recent weather.
Swimming is generally possible in designated recreation areas of Union Valley Reservoir, but it is treated as a cold, potentially hazardous environment rather than a supervised swim beach. Because the reservoir is a working water storage and recreation facility, there are often no lifeguards, and managers may post restrictions for safety, water quality, boating traffic, or operational reasons. Cold shock, sudden depth changes, submerged hazards and boat traffic are the main reasons for caution. Anyone choosing to swim should be prepared for cold water, avoid lone or unsupervised swims, and check current local advisories before entering.