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 18.9°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 |
|---|---|---|---|
| SEP 14 | 20.3°C | 23.0°C | |
| SEP 15 | 19.9°C | 23.0°C | |
| SEP 16 | 19.0°C | 23.0°C | |
| SEP 17 | 19.1°C | 23.0°C | |
| SEP 18 | 19.3°C | 23.0°C | |
| SEP 19 | 18.9°C | 23.0°C | |
| SEP 20 | 18.8°C | 23.0°C | |
| SEP 22 | 23.0°C | 19.1°C | |
| SEP 23 | 23.0°C | 19.3°C | |
| SEP 24 | 23.0°C | 19.5°C | |
| SEP 25 | 23.0°C | 19.7°C | |
| SEP 26 | 23.0°C | 19.9°C | |
| SEP 27 | 23.0°C | 20.1°C | |
| SEP 28 | 23.0°C | 20.3°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 | 3°C | 6°C |
| February | 0°C | 3°C | 6°C |
| March | 1°C | 5°C | 8°C |
| April | 4°C | 9°C | 14°C |
| May | 10°C | 15°C | 20°C |
| June | 17°C | 21°C | 24°C |
| July | 21°C | 24°C | 27°C |
| August | 22°C | 25°C | 29°C |
| September | 19°C | 23°C | 27°C |
| October | 14°C | 17°C | 20°C |
| November | 5°C | 10°C | 14°C |
| December | 0°C | 3°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 Michigan experiences typical temperate-lake seasonal water temperatures that vary with air temperature, depth and sunlight. In spring the surface commonly ranges from about 45–60°F (7–16°C) as the lake thermally stratifies, rising through late spring and early summer to roughly 60–70°F (16–21°C). Peak summer surface temperatures in July and August often reach about 70–80°F (21–27°C) in warm years, although deeper or shaded areas remain noticeably cooler. By early fall surface values usually fall back into the 60s°F (around 16–20°C) and by late fall to winter the lake approaches near-freezing conditions around 32–40°F (0–4°C); parts of the lake can ice over in cold spells.
Swimming in Union Lake is commonly practiced from private shorelines and public access points when conditions are safe and water quality is acceptable. There is no blanket statewide ban on swimming in inland lakes, but access can be limited by private property, local rules or temporary advisories. Health and safety considerations — including blue‑green algal blooms, elevated bacteria counts after heavy rains, cold-water shock early or late in the season, and ice cover in winter — are the usual reasons authorities or landowners may restrict swimming. Always check local notices and use caution when entering the water.