Originally Posted by
TXRunner78
Tough part is you never know what weather you are going to have in Sacramento in October. It could be 90 degrees and then it could be 50 degrees. The American River is a cold river. The water comes from snow melt in the nearby mountains and also from bottom of the Folsom Reservoir, which is cold. Even if it's hot, it will definitely be a wetsuit legal swim.
I have a wet suit, I can deal with cold water so long as it's over about 55*. I may not like 90* weather but it wouldn't be too bad on the bike, and by the time I get to the run it will be getting late in the day anyway. More than anything, I would worry about wind and/or rain.