A welcome dip in temperatures is on the way in your Monday forecast, but the source of that cooling will also bring elevated fire danger to portions of northern California today and Tuesday. The high pressure to our east that spurred the dangerous heat over the last week is breaking down as low pressure has developed off the coast of California. This will result in slightly cooler high temperatures across northern California today, and the threat of thunderstorm activity in the northern Sierra and southern Cascades this evening through Tuesday morning. The threat of thunderstorms has prompted a Red Flag Warning and a Fire Weather Watch to be issued by the National Weather Service. The Red Flag Warning is set to be in effect in eastern Lassen and Plumas Counties from 2pm through 8pm Monda, and the Fire Weather Watch will be in effect from Monday evening through 8am Tuesday morning in areas of Modoc, Plumas, and Lassen Counties. Gusty west winds will also be a factor in our elevated fire danger. Both Plumas and Lassen Counties will be under the Fire Weather Watch tonight. We will have some thin clouds brushing up across northern California today, but most of us will stay mostly sunny. Temperatures are warm for the start of your Monday, with 60's to 70's in the valley and foothills, and 40's to 50's in our mountain zones to start the day. We'll have wind out of the south to 15mph in the valley and foothills. Southwest wind to 15mph looks likely for the northern Sierra, and we could have gusts up to 30mph later today through Monday night. Humidity will dip into the upper single digits to around 20 percent this afternoon, which is up compared to the weekend. High temperatures are projected to top out in the mid 90's to low triple digits in the valley, while foothill and mountain areas end up in the 80's to 90's this afternoon.
Temperatures will fall by a few more degrees on Tuesday, but most of us will still have above average high temperatures on Tuesday afternoon. There will also be a threat of thunderstorms in Siskiyou County, which has already prompted a Fire Weather Watch from Tuesday afternoon through Tuesday evening in that area. Low temperatures will end up in the 60's in the valley and foothills, while mountain areas dip into the 40's to 50's Tuesday morning. High temperatures are projected to end up in the low to mid 90's in the valley for Tuesday and Wednesday, while mountain and foothlil areas mostly end up in the 70's to 80's. The low pressure area off the coast that's providing the modest cooling and potential for thunderstorms early this week will shift west off the coast late this week. High pressure will build back into northern California later this week, and we'll start to see an uptick in temperatures on Thursday. Valley areas will climb back into the mid to high 90's on Thursday afternoon, and we'll end up in the upper 90's to triple digits in the valley on Friday. Mountain and foothill areas will top out in the 80's to 90's for the latter half of this week.
Widespread triple digit heat will return to the valley this weekend, with dangerous temperatures currently projected to return in our forecast. High pressure will dominate the southwest through the weekend, and will also keep us very dry. The current projection puts valley areas back up into the 106 to 110 degree range on Saturday, with temperatures in the 110 to 115 degree range on Sunday. There will very likely be another Excessive Heat Warning issued if the current models hold through the week. Foothill and mountain areas will end up back in the 90's to triple digits this weekend. Make sure you stick with Action News Now for the latest conditions on fire danger, and we'll make sure to let you know if any fires are started by lightning. The dry weather will also keep fire danger high across all of northern California over the next few days. Plan ahead on taking advantage of the modes dip in temperatures over the next few days as the heat will be dangerous this weekend.