For sure, YES!  Patio heaters may be used in the rain, but keeping them from the rain will make them last longer. Outdoor electric heaters should be used with extreme care to make sure they are securely protected from rain or switched off.
Sometimes, a high-temperature cover might be quite useful in these situations. Fixed heaters cannot be relocated, and most portable heaters are too heavy to be moved when coming rains. These heaters may be shielded from the elements with a cover.