Dangerous heat will persist across northern California this week, and the threat of thunderstorms will be returning to some of our mountain areas. High pressure centered to our north continues to dominate our forecast Monday, and will continue to do so through this week. The Excessive Heat Warning remains in effect in the valley, foothills, Lassen County and Plumas County through 10pm Wednesday night. The Excessive Heat Warning has been extended through 11pm Thursday in Modoc and Siskiyou Counties. The Excessive Heat Warning remains in effect in northern Trinity County through 9pm Tuesday night. A Red Flag Warning for high fire danger is set to be in effect from 1pm through 9pm today on the west side of Siskiyou County due to localized gusty winds over very dry fuels. We also have a Fire Weather Watch that's been issued for portions of Lassend and Plumas Counties from Tuesday afternoon through Tuesday evening due to the threat of thunderstorms returning to that area. We have clear conditions overhead this morning, and will have plenty of sunshine across northern California today. Temperatures are starting out in the 60's to 70's in the valley and foothills, while mountain areas are starting out in the 50's to 60's. Most of us will have south winds up to around 15mph today, with gusts up to 20mph this afternoon. Siskiyou County will have gusts up to 35mph out of the south this afternoon and evening. Humidity will dip into the 10 to 22 percent range later today. High temperatures are projected to range from 102 to 109 degrees in the valley, 91 to 98 degrees in the foothills, and the lower 90's to around 101 degrees in our mountain zones this afternoon. The heat will be dangerous again today, and the hot temperatures paired with the very dry conditions and dry fuels will keep our fire danger in the moderate to high range this afternoon.
Tuesday is projected to be a degree or two hotter than Monday, and we'll also have the threat of thunderstorms returning to our higher elevations closest to the Nevada border. The threat of thunderstorms has prompted a Fire Weather Watch to be issued for portions of Lassen and Plumas Counties from Tuesday afternoon through Tuesday evening. Moisture drawn north into our region from low pressure to our south will be the source of this thunderstorm threat, and that will be possible through Thursday evening. High temperatures will dip by a few degrees by the end of this week as the ridge breaks down, and we start to get a little more influence from the Delta Breeze. The current forecast keeps valley aresa in the upper 90's to lower trilpe digits from Thursday through this weekend. Foothill and mountain areas will mostly have high temperatures in the 80's to 90's through this weekend. This does look to be a fairly toasty 4th of July weekend on the way, so make sure to plan accordingly. Dress for the heat, plan your outdoor activities for earlier in the day, and don't forget to stay hydrated.