The heat wave that has gripped California for a week took a dramatic turn Thursday as lightning storms sparked brush fires, knocked out power to thousands and caused downpours across the region. Forecasters said the extreme weather will continue through the weekend, with some parts of Northern California flirting with all-time record high temperatures. Lightning strikes were reported in many areas Thursday, with some sparking a series of brush fires near the 5 Freeway in the Santa Clarita Valley.