A western heat wave will shatter record highs for the second week of May and then spread some of its heat into the Plains later this week.

This heat is more of a "slow boil," building bit by bit every day. It is expected to peak Tuesday in the West with daily high temperatures expected to fall in cities like Las Vegas, Boise, Salt Lake City and Colorado Springs.

It will then spread into parts of the Plains late this week into the weekend with records possible in places like Kansas City.

Slow Sizzle

On Mother's Day, Reno, Nevada, soared to its first 90s of the year, setting a daily record high of 92 degrees. Death Valley tied its daily record of 112 degrees on Sunday.

Monday

Highs in the 90s are possible as far north as Medford, Oregon, and Rapid City, South Dakota. It could be the first 90s of the year in Salt Lake City, something that typically happens around June 1. Triple-digit heat is expected again in California's San Joaquin Valley and the Desert Southwest. Phoenix could flirt with 110 degrees, their hottest day of the year and only three days later in the calendar than their record earliest 110s, set on May 8, 1989.

Tuesday

Heat will continue to build north in the Great Basin and Plains. Nineties will surge into Idaho, Oregon, southern Kansas, western Oklahoma and western Texas.

Wednesday

Daily record highs are possible as far north as Montana Wednesday, where at least some 90s are possible.

Late Week-Weekend

Some 90s are possible into this weekend in parts of the central and Southern Plains, potentially as far north as Nebraska. Daily record highs are possible in Omaha, Kansas City and Wichita.

(MAPS: 10-Day US Forecast Highs/Lows)

What Is Causing This?

The setup here is actually pretty straightforward. We have a ridge of high pressure that is set up across the West. This means that the jet stream is pushed north across the West. The areas south of the jet stream in this ridge pattern tend to see warm temperatures and clear skies.

The stronger the area of high pressure, generally the more stable the air and the hotter the temperatures. While this high isn’t record-breaking, it is impressive. The graphic below gives a visual representation of this.

Any Relief?

We do forecast markedly cooler weather first in the Northwest, then into the Northern Rockies and Northern Plains late in the week. Highs in Salt Lake City should tumble into the 70s by Thursday.

That should also shave at least a few degrees off the heat in the Southwest later in the week, with highs in mid- to upper 90s in Las Vegas and low 100s in Phoenix.

Rob Shackelford is a meteorologist and climate scientist at weather.com. He received his undergraduate and master’s degrees from the University of Georgia studying meteorology and experimenting with alternative hurricane forecasting tools.