FNUS76 KSTO 190350 FWSSTO Spot Forecast for Thermalito Grass Lands RX...CAL FIRE National Weather Service Sacramento CA 850 PM PDT Mon May 18 2026 Forecast is based on ignition time of 1200 PDT on May 20. If conditions become unrepresentative...contact the National Weather Service. .DISCUSSION... Low RH values will continue on Wednesday, with Min RH values in the teens at the site. Winds will be light in the morning, but turn toward the SW to 5mph for the Valley/slope. Along the ridgetop winds will be out of the west throughout the day at 10-12mph. Winds shift toward the north along the ridgetop overnight and turn toward the southeast near sunrise at 6-10mph. Winds will be light on Thursday and terrain driven for direction and speed. Continued dry conditions on Thursday, with low Min RH in the teens to potential upper single digits. Conditions will be warm with highs in the 90s Wednesday and upper 90s to lower 100s Thursday. .WEDNESDAY... Sky/weather.........Sunny. Max temperature.....91-95. Min humidity........10-16 percent. Wind (20 ft)........ Slope/valley.......Light winds becoming southwest up to 5 mph late in the afternoon. Ridgetop...........West 9 to 12 mph. Mixing height.......5400 ft AGL. Transport winds.....Southwest 5 to 7 mph. CWR.................0 percent. Chance of thunder...0 percent. TIME (PDT) NOON 4 PM Sky cover.......MCLEAR MCLEAR CWR.............0 0 Chc of thdr (%).0 0 Temp............85 93 RH..............21 14 SL/VL wind......SW 3G7 SW 5G9 Ridgetop wind...W 10 NW 10 Mix hgt (ft)....2200 5400 Transport wind..SW 5 SW 7 .WEDNESDAY NIGHT... Sky/weather.........Clear. Min temperature.....60-64. Max humidity........43-47 percent. Wind (20 ft)........ Slope/valley.......South winds up to 5 mph early in the evening shifting to the east up to 6 mph, then becoming up to 5 mph overnight becoming light. Ridgetop...........North 10 to 12 mph shifting to the southeast 6 to 10 mph overnight. Mixing height.......400 ft AGL. Transport winds.....South around 6 mph shifting to the east 6 to 9 mph early in the evening. CWR.................0 percent. Chance of thunder...0 percent. TIME (PDT) 6 PM 10 PM 2 AM Sky cover.......CLEAR CLEAR CLEAR CWR.............0 0 0 Chc of thdr (%).0 0 0 Temp............92 80 69 RH..............16 27 33 SL/VL wind......S 5G8 SE 5G7 E 5G6 Ridgetop wind...NW 12 NE 10 SE 9 Mix hgt (ft)....5400 400 400 Transport wind..S 6 E 6 E 8 .THURSDAY... Sky/weather.........Sunny. Max temperature.....97-100. Min humidity........9-14 percent. Wind (20 ft)........ Slope/valley.......Light winds becoming southwest up to 5 mph late in the morning, then shifting to the south late in the afternoon. Ridgetop...........South 3 to 6 mph shifting to the north in the afternoon. Mixing height.......6200 ft AGL. Transport winds.....Northeast 3 to 6 mph shifting to the southwest 5 to 8 mph late in the morning. CWR.................0 percent. Chance of thunder...0 percent. TIME (PDT) 6 AM 10 AM 2 PM Sky cover.......MCLEAR MCLEAR CLEAR CWR.............0 0 0Chc of thdr (%).0 0 0 Temp............64 78 94 RH..............45 34 19 SL/VL wind......NE 2G3 N 0G2 SW 5G9 Ridgetop wind...S 6 W 2 N 1 Mix hgt (ft)....400 800 5500 Transport wind..E 6 NE 3 SW 7 $$ Forecaster...JS Requested by...Tim Cassone Type of request...PRESCRIBED .TAG 2613944.0/STO .DELDT 05/19/26 .FormatterVersion 2.0.0 .EMAIL tim.cassone@fire.ca.gov