They are fed mainly by snow melt and water temperatures are very cold in both spring and summer. The danger of hypothermia is very real and needs to always be considered on any boating adventure. Individuals have lost their lives while boating in the park, even while wearing personal floatation devices, due to hypothermia. The second thing to be aware of and consider, are storms and winds. The winds on Yellowstone's Lakes can be and usually are very strong or harsh almost daily.
Thunderstorms materialize very quickly, the weather is very unpredictable.
Please do not attempt to cross lakes in small water crafts - rowboats or canoes. The weather and wind may be calm and nice when you start on the water, but storms can appear quickly with no warning, putting your life and anyone with you in danger. It is recommended that you travel early in the morning and stay within 100 yards of the shore. There is usually less wind activity during the morning and if a storm appears, you can head for shore and cover. Use the afternoon and evening hours to explore inland.