It's hot. At least by Portland's spring standards.

The city broke into the 70s on Monday for the first time in 2018, and it may see record-breaking heat over the next two days.

And with plenty of sun in the forecast through Thursday, 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.

The region has already experienced at least one drowning this year. A 24-year-old Klamath Falls man died while swimming in the Lewis River in northern Clark County last week, authorities said. Cold water was suspected to have contributed to his death.

The Oregonian/OregonLive tracks drownings in public, natural waterbodies in Oregon and southwest Washington for Memorial Day weekend through Labor Day weekend. Eighteen people died in 2017, down from 21 the year before.

Those figures are both less than the 36 deaths recorded in 2015 -- the deadliest year on record since 2006, when 41 died. Early-season swimming can be more dangerous than summer swimming because of colder water temperatures and river currents quickened by snowmelt.

If you choose to 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.

While it will be warm this week, which will make area rivers inviting, please remember that many rivers are still cold enough to produce cold water shock & hypothermia. Remember to wear a life jacket if you plan on playing on or in the water this week #pdxtst #orwx #wawx pic.twitter.com/1N7PG85WrN — NWS Portland (@NWSPortland) April 22, 2018

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 shock swimmers, cause a lack of muscle function in their limbs and make it exceptionally difficult for them to swim to safety.

And while highs near 81 and 85 are expected in Portland over the next two days -- both of which would set daily records -- river temperatures are much colder. The Willamette River in Portland, for example, was about 53 degrees Monday afternoon.

Looking at our records we have:

Earliest 1st 80° day: Mar 16, 1947

Avg 1st 80° day: May 8th

Latest 1st 80° day: Jun 12, 2010



Last year PDX 1st 80° day was: May 3rd — NWS Portland (@NWSPortland) April 23, 2018

The Clackamas River near Oregon City -- not far from Gladstone's popular High Rocks Park -- was 51.6 degrees later that afternoon. And the Columbia River in Washougal was about 51 at 5 p.m.

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