CoCoRaHS is Coming to California - CoCoRaHS, Co mmunity Co llaborative Ra in, H ail and S now Network, will expand into California this month, joining 35 states that are already participating in this program. This is a volunteer network of backyard weather observers of all ages and backgrounds working together to measure and map precipitation (rain, hail, and snow) in their local communities. For more information on this program, please visit the National CoCoRaHS Website or the State of California CoCoRaHS Website . To become a CoCoRaHS observer, use the online application.