A Zeer Pot is an ancient device used to cool things. It was invented by the Egyptians about 2500 years before Christ was born. It works on the principle of evaporative cooling. It’s still in use today in North Africa.
Interesting notes: More wind speed can improve cooling efficiency. Hotter air flowing over the pot might improve the efficiency. Airflow coming off a hot parking lot might improve efficiency if your pot is in the shade because hotter air can hold more moisture which means that it can increase evaporation of the pot’s moisture.