The Seattle-Tacoma metro area is the least air-conditioned place in the United States, and many of us have paid the price during this unseasonable stretch of 90- and 100-degree days.

At times like this it’s easy to forget we have an awesome natural cooling feature in our backyard. Roughly 35 square miles of glacial ice and snow mass cover the flanks of 14,411-foot-tall Mount Rainier, which Pierce County folks cherish as “our” mountain.

Seasonal snowmelt from Washington mountain ranges is needed to keep water cold, regulate stream flows, produce reliable electricity and irrigation, and nourish life-sustaining habitat for fish and other species.

Trouble is, the impact of excessive temperatures on Mount Rainier’s glaciers is as real as the pressure on your household air conditioner, with one big difference: It won’t subside when this heat wave ends.

The relentless force of human-caused global warming has made sure of that.

As June goes out like a lion, with Monday’s temperatures at Paradise hitting near 90 degrees and Longmire pushing past 100, it portends a summer that experts say will be hotter and drier than normal.

That doesn’t bode well for Mount Rainier’s 25 glaciers. They’ve already given up more than one-third of their coverage and 45 percent of their thickness since 1900, according to research by Mount Rainier National Park geologist Scott Beason.

“I’ve been in the park full time since 2010, and I’ve never seen anything like this,” Beason said Monday, as he braced for a third day of intense early-summer heat.

The resulting meltoff has filled the Nisqually and other glacier-fed rivers and streams to their banks with turbid water resembling chocolate milk.

“There’s a long-term trend of glacier recession, and events like this don’t help,” he added.

Over the weekend, the National Weather Service office in Seattle issued advisories for an “unprecedented heat event.” Forecasters warned of high fire risks, heat-related illnesses, drownings, power outages — all urgent concerns for Puget Sounders coping with this scorch fest one day at a time.

But the fine print was also important, certainly for our state’s long-term livability; it warned of “significant impacts” on mountain snow and glaciers.

Beason said the snow’s been melting 6 to 7 inches a day at the terminus parts of Mount Rainier’s glaciers, triple its normal rate this time of year. The forecast at Paradise is a snowpack depth of 29 inches by the end of June; that’s 20 inches less than the historic average from 1917 to 2020.

While the heat breaks records now, Beason said the effects will be more severe if it returns later this summer, when temperatures typically spike. By then, the early-season snow layer that helps fasten rocks and chunks of ice to the upper mountain will have vanished.

“If we get this later in the year, all the seasonal stuff will be gone and you’ll be melting ice at that point,” Beason said.

The mountain is then more likely to release debris flows, disgorging material built up over centuries of glacial activity, clogging stream channels with sediment and reshaping the lowlands as far as where the Puyallup River meets Tacoma’s Commencement Bay.

You don’t need a doctorate in geophysics to grasp the worst-case scenarios of our mountain losing her glaciers. Anyone here for the flood of 2006, which washed out campgrounds, closed the park for six months and permanently closed the Carbon River Road to cars, knows how swiftly heavy precipitation can lead to ruinous torrents.

With storm season months away, any threat to the mountain posed by this heat wave may seem remote. Hikers, climbers and other outdoor enthusiasts might welcome the early melt-off, since it speeds access to prime destinations like the Wonderland Trail.

For all who work and play on Mount Rainier, warnings about high-water crossings and collapsing snowbridges are top of mind as June turns to July.

But let’s not lose sight of the existential threat of climate change. Steps taken by state lawmakers the last few years, such as adopting a clean-fuel standard and a net-zero greenhouse gas emission goal by 2050, set an ambitious tone.

We shouldn’t let our commitment to stop burning fossil fuels blow hot and cold. At a time when Washington’s glaciers are retreating, our policy makers must not.

The News Tribune is based in Tacoma, Washington.