Weather for Little Grass Valley Reservoir, CA - Little Grass Valley Reservoir, CA Weather, Current Weather in Little Grass Valley Reservoir, CA. Local weather report for Little Grass Valley Reservoir, CA, Local Little Grass Valley Reservoir, CA weather. Forecast for Little Grass Valley Reservoir, California, Little Grass Valley Reservoir, CA weather forecast. Find your local Little Grass Valley Reservoir weather forecast. Little Grass Valley Reservoir, CA weather conditions.