Union Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Union Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Union Lake today is 22.9°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 |
|---|---|---|---|
| SEP 14 | 24.7°C | 22.9°C | |
| SEP 15 | 24.5°C | 22.9°C | |
| SEP 16 | 24.7°C | 22.9°C | |
| SEP 17 | 23.8°C | 22.9°C | |
| SEP 18 | 22.8°C | 22.9°C | |
| SEP 19 | 22.9°C | 22.9°C | |
| SEP 20 | 23.6°C | 22.9°C | |
| SEP 21 | 22.9°C | 22.9°C | |
| SEP 22 | 22.9°C | 22.9°C | |
| SEP 23 | 22.9°C | 22.9°C | |
| SEP 24 | 22.9°C | 22.9°C | |
| SEP 25 | 22.9°C | 22.9°C | |
| SEP 26 | 22.9°C | 22.9°C | |
| SEP 27 | 22.9°C | 22.9°C | |
| SEP 28 | 22.9°C | 22.9°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 | 7°C | 12°C |
| April | 8°C | 14°C | 20°C |
| May | 13°C | 19°C | 25°C |
| June | 15°C | 23°C | 30°C |
| July | 23°C | 28°C | 33°C |
| August | 22°C | 27°C | 31°C |
| September | 20°C | 23°C | 26°C |
| October | 12°C | 17°C | 21°C |
| November | 5°C | 9°C | 12°C |
| December | 3°C | 5°C | 7°C |
Union Lake: Water Temperature by Location
Union Lake: Weather Forecast
September 21
September 22
September 23
September 24
September 25
Location & Local Information
Union Lake in New Jersey experiences typical northeastern seasonal water temperatures. In winter the surface often sits near freezing, roughly 32–40°F (0–4°C). During spring temperatures climb from about 40–60°F (4–16°C) as the lake stratifies and thaws. Summer brings the warmest conditions, with common surface readings between 70–80°F (21–27°C) and occasional warm spells pushing low-80s°F (27–28°C) on hot afternoons. By early fall the water cools back into the 60–70°F (16–21°C) range before descending toward winter values. Bottom temperatures remain cooler year-round, and variation by year, depth, and wind or rainfall can shift these ranges by several degrees.
Swimming at Union Lake depends on local rules, access points and current water quality. Where municipal beaches or designated swim areas exist, swimming is typically allowed in summer when temperatures are comfortable and lifeguards or signage are present. In other parts of the lake, swimming may be restricted for reasons such as private ownership, safety hazards, poor water clarity, or harmful algal blooms. Cold spring or late-fall waters also pose risks of cold-water shock even if technically accessible. Visitors should check local postings or township guidance and heed posted advisories before entering the water.