Pattern Change This Week to Keep East Relatively Cool as a Heat Wave Moves Into Parts of the West

Chris Dolce
Published: June 12, 2019

Much of the East will be relatively cool for June as intense heat persists in the West from a weather pattern change that has developed across the Lower 48.

The jet stream has amplified, as it takes a pronounced southward plunge east of the Rockies. When that happens, the jet stream tends to build northward in the West. This is somewhat unusual for this time of year since the jet stream typically runs in a flatter west-to-east fashion near the Canadian border during the summer months.

As a result, this week's forecast has contrasting temperatures from coast to coast. Rainy conditions will also continue to plague parts of the East.

The jet stream is diving southward in the East, keeping temperatures cool for June standards. Meanwhile, it is lifting northward in the West, allowing hot temperatures to build.

Cool and Wet East

An initial shot of cooler and drier air will chase most of the early-week rain out of the East into Wednesday. That will be followed by another reinforcing shot of cooler air in the central and eastern states during the second half of this week.

All this means is that temperatures will run near or below average for mid-June in many areas east of the Rockies this week.

Much of the Midwest, Great Lakes and Northeast will have highs in the 70s through at least Friday. Temperatures may not get out of the 60s in those regions on some of the days.

In the South, highs in the upper 70s and lower 80s can be expected for much of the region. Drier air will even grip the South, giving a brief break from the high humidity that is typical this time of year.


Forecast Highs

This weather pattern won't be completely dry, however.

More showers and thunderstorms will spread across the Midwest and East Wednesday through Friday.

(MORE: Daily Forecast Maps)

West Heats Up

Hot temperatures will grip areas from the Pacific Northwest into the Desert Southwest as the jet stream builds northward.

Phoenix is likely to see its first 110-plus-degree temperatures of the year Wednesday.

Highs in mid- to upper 90s are forecast as far north as Portland, Oregon, through Wednesday. Even Seattle may flirt with 90 degrees Wednesday. Temperatures will trend cooler in the Northwest by late in the week as the jet stream begins to flatten out.

Daily record highs could be threatened in a few locations through midweek. This includes Portland and Phoenix on Wednesday; the current daily records for June 12 are 93 degrees and 112 degrees, respectively. Death Valley, California, could reach 120 degrees for the first time this year.

San Francisco (downtown) tied its daily record high of 91 degrees on Sunday afternoon, then set new daily record highs on Monday (97 degrees) and Tuesday (92 degrees). This was the hottest 3-day stretch in meteorological summer (June through August) on record.

San Francisco International Airport reached 100 degrees on Monday, also a record high for the date at that climate site and the first time it has ever hit the century mark in any month other than September, according to Scott Rowe, a meteorologist at the National Weather Service.

Monterey, California, set a new all-time record high for meteorological summer (June-August) on Monday, when it topped out at 97 degrees at the airport. The previous all-time record between June and August was 94 degrees, according to Philippe Papin, an atmospheric scientist at the U.S. Naval Research Laboratory in Monterey. This also smashed the daily record high for June 10, which was only 77 degrees.

Eureka, California, tied its June hottest temperature of 85 degrees on Tuesday.

More than a dozen daily record highs were set or tied Tuesday in the Bay Area alone. Among them included Oakland International Airport (99 degrees), San Francisco International Airport (98 degrees) and Monterey (92 degrees). Portland, Oregon, also set a daily record high on Tuesday of 96 degrees.


Forecast Highs

Daily record warm low temperatures are also possible through Thursday from Seattle to Southern California and Las Vegas.

The hot weather through midweek has prompted the National Weather Service to issue excessive heat warnings and heat advisories from southern Arizona into California, southern Nevada, western Oregon and southwestern Washington.


Heat Alerts

Be sure to take precautions if your location is forecast to see extreme heat this week.

(MORE: Four Things Extreme Heat Does to Your Body


The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.