Thunderstorms have visited the Imperial Valley and parts of eastern San Diego County over the past several weeks. The seasonal arrival of moisture from the east and south, more or less typical for late summer, contributes to the greening of certain kinds of vegetation. On the desert floor, for example, the spidery ocotillo can grow an instant crop of green leaves after a storm, only to drop them two to three weeks later if no further rain arrives. The distribution of green-leaved ocotillos tells not only where rain has recently fallen, it also indicates where the runoff has collected and remained for enough time to be absorbed by the ocotillo’s root system.
Shore Birds migrating southward are beginning to arrive in San Diego County. Through fall and winter various ducks, sandpipers, and plovers will be spotted in increased numbers in the county's remaining coastal wetlands. Best bird-watching spots include the Tijuana River estuary, south San Diego Bay, the San Diego River flood channel, Peñasquitos Lagoon, San Elijo Lagoon, Batiquitos Lagoon, and Buena Vista Lagoon.