This is going to end up shorter than I would have wanted today. Expect a more full report Wednesday.
A large expanse of arctic air is invading all the West and will have no greater effect on perhaps millions and millions of people than the cold that is expected in farm-rich California. There is the huge risk for many of the tender vegetable crops grown on the Central Coast, and farther inland, the vast citrus groves are facing potential devastating effects on oranges and lemons.
Two shots of cold air are coming. One is arriving Tuesday night and Wednesday and will be around into Friday. The coldest times will be Thursday and Friday mornings in the big agricultural areas. Widespread frost is likely to the coast and widespread freeze to hard freeze is likely farther inland along the coast and into the Central Valley. Places like Salinas Valley, San Luis Obispo and surrounding areas are going to dip into the middle and upper 20s. Paso Robles will be closer to 20 and it could be upper teens Friday morning. In the citrus areas from the San Joaquin Valley to northern Ventura County, expect a hard freeze in most areas with the coldest San Joaquin Valley locations dipping down to 20 to 25 for more than a few hours.
Friday night into Saturday, a disturbance moving from north to south across California will hold temperatures up Friday night but also cause a few showers with very low snow levels. Snow levels could be down to 1,500 to 2,000 feet. Behind this low, the air mass will get even colder on Sunday than it will be Thursday into Friday, so temperatures Sunday night can be a few degrees lower than Friday morning.
The very cold air is likely to extend down into all of southern California as well. The big growing areas of the Coachella Valley can have areas of frost Thursday and Friday morning but local freezing temperatures Monday morning.
I will go more into this on Wednesday.
As of the end of June there had been no named storms in the Eastern Pacific basin.
This is some serious and dangerous heat. Outdoor activity is just not at all recommended during the daytime.
A strong ridge of high pressure in the West brings the highest heat of the season so far to a large area.
Combine the cold with the wind and some precipitation and there is a real danger of hypothermia.
Any shower and thunderstorm can contain heavy downpours, heavy enough to cause temporary, low-lying ponding.
According to all long-range models, the warmest area in North America compared to average will be over the Northwest.