What is the ET rate referred to on the weather page of the website, and how do I use it?
ET stands for evapotranspiration. It is the combination of two processes whereby water is lost from the soil-evaporation into the air, and transpiration through plants. ET is calculated by measuring solar radiation, temperature, and humidity and is figured for a crop that is well watered and managed. The reference crops are either grass or alfalfa – either works well for our climate. Use ET by applying the amount of irrigation water called for on the chart for that day. For example: an ET of 0.25 means the recommendation is one quarter inch of water. Unfortunately, the system does not take into account what may have happened the day before, and in fact, depending on when you are reading it, may not be accurate indicator for that day. If you read the ET at 6 a.m. in the morning it may still be low due to temperature, since it is measuring since midnight. A very dry day to follow will likely indicate a higher ET, and if you don’t read the chart again after it’s been hot and dry, you won’
