Electronic devices designed to operate in outdoor conditions must be resistant to rain and moisture. In such cases, we use hermetic enclosures that provide protection against adverse weather conditions. However, even with the best enclosures, there is always a risk that water may enter the device. Therefore, we always leave a small hole with a diameter of 1-2 mm at the bottom of such enclosures to allow for ventilation.
This intentional design allows the water to evaporate before it can cause any damage inside the device. Often, when water gets inside, it remains there permanently, which is why the presence of a small hole allows it to naturally drain out. Full hermetic sealing is only necessary for devices operating underwater or exposed to strong water streams.
In conclusion, using hermetic enclosures with a small hole at the bottom provides protection for electronic devices against moisture and rain while allowing any potential water inside to escape before causing damage.