Rainbow Lake — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Rainbow Lake, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Rainbow Lake today is 18.7°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 | 19.6°C | 18.6°C | |
| SEP 15 | 19.5°C | 18.6°C | |
| SEP 16 | 19.0°C | 18.6°C | |
| SEP 17 | 19.6°C | 18.6°C | |
| SEP 18 | 18.9°C | 18.6°C | |
| SEP 19 | 19.2°C | 18.6°C | |
| SEP 20 | 19.0°C | 18.6°C | |
| SEP 21 | 18.7°C | 18.6°C | |
| SEP 22 | 18.6°C | 18.7°C | |
| SEP 23 | 18.6°C | 18.7°C | |
| SEP 24 | 18.6°C | 18.7°C | |
| SEP 25 | 18.6°C | 18.7°C | |
| SEP 26 | 18.6°C | 18.7°C | |
| SEP 27 | 18.6°C | 18.7°C | |
| SEP 28 | 18.6°C | 18.7°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 | 0°C | 1°C | 3°C |
| February | 0°C | 2°C | 4°C |
| March | 0°C | 3°C | 6°C |
| April | 1°C | 7°C | 14°C |
| May | 8°C | 14°C | 21°C |
| June | 16°C | 20°C | 24°C |
| July | 19°C | 24°C | 29°C |
| August | 20°C | 25°C | 30°C |
| September | 14°C | 19°C | 24°C |
| October | 9°C | 14°C | 18°C |
| November | 3°C | 9°C | 14°C |
| December | 0°C | 2°C | 4°C |
Rainbow Lake: Water Temperature by Location
Rainbow Lake: Weather Forecast
September 22
September 23
September 24
September 25
Location & Local Information
Rainbow Lake in northern Wisconsin experiences a strong seasonal cycle in water temperature. In winter the lake is typically ice-covered and surface temperatures hover at or very near freezing, about 32°F (0°C), with deeper water remaining just above freezing in the mid-30s°F (1–4°C). During spring the surface warms through the 40s and 50s°F as the ice melts and the water mixes, roughly 4–16°C. By summer the shallow, sunlit surface layer commonly reaches the upper 60s to upper 70s°F, approximately 20–26°C, while deeper layers stay noticeably cooler due to stratification. In autumn the surface cools again, moving from the 60s into the 40s°F (about 16–4°C) as turnover occurs and the lake returns toward winter conditions.
Swimming is generally allowed during the ice-free months, and many people do swim when surface temperatures are in the comfortable summer range. However, access and use can be limited by local rules, water-quality advisories (for example, elevated bacteria or cyanobacteria blooms), or safety concerns such as lack of lifeguards and cold water shock in cooler seasons. Because deeper water and early/late season temperatures can feel quite cold, swimmers should be mindful of hypothermia risk, check current advisories before entering the water, and take ordinary safety precautions.