Dry air helps a cooler work, while humid days change the result.
An evaporative cooler lowers air temperature by adding water to it. Clyde's often-dry conditions give that process room to work, because dry outdoor air can absorb more moisture as it passes through wet pads. The cooler's output changes after rain and during humid weather, when the air already holds more moisture and there is less temperature drop to gain.
Dust affects the equipment itself as well as the air moving through it. It builds up in pads, restricts airflow, and puts added strain on the pump and blower. We inspect pad condition, water distribution, pump operation, the belt and blower, float adjustment, and the water lines and drain to find where cooling or airflow is being lost.
The house also needs a deliberate route for indoor air to leave. An evaporative cooler brings in outside air rather than recirculating sealed indoor air, so a tightly closed house without a relief opening holds that air in and limits how well the system performs.