Best lakes to swim in December

How we pick

We start from U.S. lakes rated 4.3★ or higher across 100+ Google reviews and look for a monitoring station named for the same lake in the Water Quality Portal (USGS, EPA and state agencies). We keep only lakes with a swim beach or swimming allowed — checked against the operator’s rules where the listing doesn’t say — which leaves 62. Rules change and some areas close seasonally, so check with the park or lake operator first. Each month’s figure averages near-surface readings since 2010, counting the warmest reading of each sampling day, and needs at least three sampling days. A lake makes the list at 70°F or warmer — below that, sudden entry risks cold shock — ranked by a review-weighted rating, at most two per state. Monitoring is irregular, so treat these as typical, not exact.