Rainlog.org is a cooperative rainfall monitoring network for Arizona developed at The University of Arizona by SAHRA (Sustainability of semi-Arid Hydrology and Riparian Areas) and the school's cooperative extension. Data collected through this network will be used for a variety of applications, including watershed management activities and drought planning at local, county and state levels.

Official rain gauges in Arizona are few and far between. The large gaps in coverage are a particular problem where precipitation amounts are highly variable due to topography and seasonal weather patterns. This is especially true during the monsoon season, when thunderstorms can produce heavy rainfall that is very localized.

All data posted by volunteers is available in real-time in maps useful in tracking high-resolution variability in precipitation patterns and potential changes in drought status. As more people participate and more information is gathered, the resolution of the maps will improve.

Citizen scientists are asked to track daily or monthly precipitation amounts. Daily observations should ideally be recorded as close to 7 a.m. as possible. Each daily observation will cover the previous 24 hours and represent the previous calendar day. This is consistent with the National Weather Service Cooperative Observer Program monitoring protocol.