Mercer County Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Mercer County Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Mercer County Lake today is 29.7°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature is above 82°F (28°C). This is very warm water, which may feel almost hot to most people. Swimming in such conditions is perfect for those seeking relaxation and comfort in the water. These waters are often preferred for relaxation in hot weather, as the water temperature does not cool the body significantly. However, it is important to remember that in such warm waters, caution is necessary, as prolonged exposure without rest can lead to overheating. 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 |
|---|---|---|---|
| JUL 14 | 25.8°C | 28.5°C | |
| JUL 15 | 28.8°C | 28.5°C | |
| JUL 16 | 28.8°C | 28.5°C | |
| JUL 17 | 29.1°C | 28.5°C | |
| JUL 18 | 29.1°C | 28.5°C | |
| JUL 19 | 29.1°C | 28.5°C | |
| JUL 20 | 29.1°C | 28.5°C | |
| JUL 21 | 28.8°C | 28.5°C | |
| JUL 22 | 28.5°C | 29.6°C | |
| JUL 23 | 28.5°C | 29.6°C | |
| JUL 24 | 28.5°C | 29.5°C | |
| JUL 25 | 28.5°C | 29.5°C | |
| JUL 26 | 28.5°C | 29.4°C | |
| JUL 27 | 28.5°C | 29.3°C | |
| JUL 28 | 28.5°C | 29.3°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 | 0°C | 4°C | 7°C |
| February | 0°C | 4°C | 7°C |
| March | 1°C | 6°C | 10°C |
| April | 9°C | 15°C | 20°C |
| May | 15°C | 19°C | 23°C |
| June | 16°C | 23°C | 30°C |
| July | 24°C | 29°C | 33°C |
| August | 23°C | 27°C | 31°C |
| September | 20°C | 23°C | 25°C |
| October | 12°C | 17°C | 21°C |
| November | 5°C | 9°C | 13°C |
| December | 2°C | 5°C | 7°C |
Mercer County Lake: Water Temperature by Location
Mercer County Lake: Weather Forecast
July 22
July 23
July 24
July 25
Location & Local Information
Mercer Lake, in Mercer County Park, typically follows the seasonal temperature patterns of shallow temperate lakes in central New Jersey. In winter the water commonly ranges from about 34–40°F (1–4°C) and can approach freezing in cold spells. Spring sees a steady rise, often 40–60°F (4–15°C) as the surface warms. Peak summer surface temperatures commonly reach the high 60s to high 70s °F (around 20–26°C) and can occasionally climb into the low 80s°F (27–28°C) on hot, calm days; deeper water remains noticeably cooler due to thermal stratification. In autumn the lake cools again, with surface temperatures typically falling into the 50s–60s°F (10–18°C). Actual readings vary year to year with air temperature, wind, and rainfall.
Public swimming is generally not permitted at Mercer Lake. The restriction is driven by safety and management considerations: there are no lifeguarded, designated swimming beaches, the lake supports boating and rowing traffic, and underwater hazards and variable water quality (including the occasional algal bloom or cold-water pockets) create added risk. Visitors seeking open-water recreation commonly use the lake for non‑swimming activities such as paddling and fishing, while designated municipal or state beaches in the region offer supervised swimming opportunities when available.