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