West Coast residents could be forgiven for rubbing the sweat out of their eyes and staring in disbelief at both their thermometers and their calendars this week: 100 degrees? In June?

A heat wave has punctured any expectations of a mild spring, with millions of people sweltering through blistering temperatures in cities like Las Vegas (102 degrees), Sacramento (103) and Phoenix (109).

Temperatures at San Francisco’s airport surged into the triple digits on Monday, a record for this time of year, the National Weather Service said. Other milestones included a new daily high of 97 degrees in Portland, Ore., and 106 degrees in Modesto, Calif., both set on Tuesday.

The scorching weather has plagued firefighters battling dozens of wildfires, caused major transit delays and forced many to ask just what is going on?

Here are some answers:

Why is it so hot?

A northward bulge in the jet stream thousands of feet above our heads has meant that warmer air has flowed from the south to the north, said Dr. Jennifer Francis, a senior scientist at the Woods Hole Research Center who studies climate change and its effects on weather.

Bulges in the jet stream occur naturally, but there are indications that they are happening more frequently, she said, in part because of warming waters in the Bering Sea and throughout the northern Pacific Ocean.

So is there a connection to climate change?

Experts caution that it is difficult to definitively tie any one event to climate change, but the early heat fits with trends predicted by climate change models.

“The question really is whether this is happening more often or whether there’s a connection to climate change,” Dr. Francis said. “The answer to that is probably yes.”

She added that an unusually wavy jet stream pattern can also cause extreme weather elsewhere, like flooding in the Midwest and warm temperatures in the Southeast.

Does this spring heat wave increase the threat of wildfires?

Scott McLean, a spokesman for the California Department of Forestry and Fire Protection, known as Cal Fire, said firefighters “watch the weather religiously” and think this summer could be as bad as the last, when blazes, including California’s largest ever, ravaged the state.

“There’s really no reason to think it’ll be different — the potential is there,” he said.

Pacific Gas & Electric, the utility that has filed for bankruptcy and whose power lines sparked California’s deadliest wildfire, turned off thousands of customers’ electricity over the weekend to avoid potential wildfires.

What’s the best way to stay safe in the heat?

Signs of heat exhaustion include faintness or dizziness, clammy skin and cramps or fatigue.

The National Weather Service urges people in sweltering regions to drink lots of water, check on older people and those without air-conditioners, and to avoid difficult, outdoor tasks if possible.

The service also warns against locking toddlers, older people or animals in a car. (In California, it is legal to break a car window out of concern for a cat or dog’s health in the heat.)

When will there be relief?

The scorching temperatures were beginning to fall for much of the coast on Wednesday, but the Seattle area was still predicted to match its record high.

In the Bay Area, where one television station recorded the temperature inside a Bay Area Rapid Transit car at 107 degrees this week, temperatures should fall to the 70s and 60s for the rest of the week.

But the entire West Coast, as well as Nevada and Arizona, will probably see temperatures above historical averages over the next three months, according to the National Weather Service’s Climate Prediction Center. Temperatures generally fluctuate throughout the summer and, for much of the West Coast, peak in late August or September.

Source: Read Full Article