You will be swimming in spring-fed pools, which are QUITE chilly any time of year! So you will want to pick a time that at least there will be warm sunshine when you come out. I took a brisk but enjoyable dip on a warm day in late October, even though it got down into the 40s that night.
Warmer weather is best.
During hunting season they close the park and you can't go hiking after dark because of the mountain lions. They are ambush predators so when you go travel in a group if two or more. Deep summer in Texas can be hard if youre not experienced, and since Colorado bend is a dead zone for cell service so keep that in mind when you go out there. I have gone swimming there between the months of March and November.
Wait till deep summer to enjoy
You can swim in the designated area. You can also tube the river and rent kayaks. It's cold tho.
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