In order to get an accurate reading and to prolong the life of your transmitter, we recommend that you have it in a sheltered area out of the sun and direct rain. Fog and Mist will not affect the sensor, but a soaking in water may. You can mount it outside under an eave of your house or any other suitable place that will keep it out of the sun and rain. Do not wrap the sensor in plastic or seal it in a plastic bag.