- The chart below, from City of Ventura Water website, applies to Coastal Zone cities like Oxnard, Port Hueneme, Ventura, Carpenteria and Santa Barbara
Ojai and Santa Paula are inland, so it is hotter, meaning higher evapotranspiration rate (Ojai is similar to Santa Paula, which is our closest weather station, at ETO of 55), meaning more water is required than coastal cities.
The unpredictable “climate chaos” makes it difficult to predict the “right” amount of water to apply. Typically, we overwater our landscapes, because it is hard to know how much to water—it is complicated to figure out. It is based on evapotranspiration rates, that are determined by climate data such as heat, humidity, wind, and they are based on amount of water is takes to keep grass looking good, which is set at 100% of ETo. Everything else is calibrated off of the amount of water it takes to grow turf grass.
When plants look stressed, we tend to add water and fertilizers to try to help them. Since rain water is scarce these days, it is good to challenge plants to dig deeper roots. That means deliberately using less water, watching plants closely, and looking for signs of under watering like curled leaves, wilted leaves, and leaves turning color. Plants that are deciduous need very little water.
For more info on watering, see Four Signs You are Overwatering Your Plants
To determine how much water your plants really need, identify plant genus, species or common name and look plants up on WUCOLS IV which assigns plants to High, Medium, Low and Very Low water requirement by zones. Ojai is in Zone 4, Ventura is in Zone 3.