Portland-area rivers and lakes may look like an enticing way to beat the heat.

But water temperatures are still chilly, and that can present danger to anyone looking to take a dip. Entering cold water can cause swimmers to gasp, inhale water then go under. Currents can keep swimmers from reaching safety.

This weekend, a Portland man went missing after falling out of an inner tube during a weekend floating trip on the Washougal River, according to the Clark County Sheriff’s Office. Authorities searched for him Sunday, but he remains missing.

Early-season swimming and other water activities can be more dangerous because of colder water temperatures and river currents quickened by snowmelt.

If you swim, officials urge awareness of water temperatures and hazards, wearing life jackets and refraining from drinking alcohol. Swimmers should also keep an eye on children near the water, abide by posted rules, swim with others and be aware of their swimming skill, officials say.

"Wearing a properly fitting life jacket, that would be the No. 1 thing" to stress when teaching people about water safety, Sgt. Bob Ray of the Washington County Sheriff's Office previously told The Oregonian/OregonLive.

That's in addition to not overestimating your swimming ability and refraining from drinking or smoking marijuana while enjoying the Northwest's waterways.

Such warnings are commonplace as temperatures rise and lakes and rivers exert a seemingly gravitational pull on swimmers. Cold water -- which can seem warm near the surface -- can quickly and unexpectedly cause a lack of muscle function in limbs.

And while highs are expected to crest near 89 degrees this week, river temperatures are much colder. The Willamette River in Portland, for example, was about 57 degrees Monday afternoon.

The Clackamas River near Oregon City -- not far from Gladstone's popular High Rocks Park -- was under 53 degrees. And the Columbia River in Washougal was less than 56 degrees.

The nonprofit National Center for Cold Water Safety advises people to treat any water temperature under 70 degrees with caution.

-- Jim Ryan; jryan@oregonian.com; 503-221-8005; @Jimryan015

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