Water temperature by month
| Month | Average Temperature (°F) | Average Temperature (°C) |
|---|---|---|
| January | 39.64 | 4.24 |
| February | 39.07 | 3.93 |
| March | 39.27 | 4.04 |
| April | 42.54 | 5.86 |
| May | 46.36 | 7.98 |
| June | 50.27 | 10.15 |
| July | 52.32 | 11.29 |
| August | 54.46 | 12.48 |
| September | 53.94 | 12.19 |
| October | 50.55 | 10.31 |
| November | 44.48 | 6.93 |
| December | 41.06 | 5.04 |
These monthly temperatures are averages of the available data from the following years: 2024, 2023, 2022, 2021, 2020.
Site location
- Latitude: 47.95926837
- Longitude: -121.7973447
- Altitude: 602.36 feet
- Altitude Accuracy: Within .11 feet
- Map: View on Google Maps
About this data
This data was sourced from the US Geological Survey, "the science arm of the Department of the Interior bringing an array of earth, water, biological, and mapping data and expertise to bear in support of decision-making on environmental, resource, and public safety issues."
- Agency: USGS
- Site Number: 12137800
- Site Name: Sultan River Below Diversion Dam Near Sultan, Wa
- Hydrologic Unit Code: 17110009
Is it warm enough for swimming?
Water temperatures can vary significantly based on the location and time of year. Generally, swimming is considered comfortable in water temperatures between 78°F (25°C) and 82°F (28°C). Cooler temperatures can be refreshing, but if the water temperature drops below 70°F (21°C), prolonged exposure can be uncomfortable without a wetsuit.
Should you wear a wetsuit?
Wetsuits provide insulation and buoyancy, making them ideal for swimming in cooler waters. Here are some general guidelines for wetsuit use:
- 70°F (21°C) and above: No wetsuit needed for most people.
- 65°F - 70°F (18°C - 21°C): A thin wetsuit (2mm - 3mm) is recommended.
- 60°F - 65°F (15°C - 18°C): A thicker wetsuit (4mm - 5mm) is recommended.
- Below 60°F (15°C): A full wetsuit with a hood, gloves, and booties is recommended for safety and comfort.