My idea is that this is a config setting. Players can turn this setting on if they want the Nether to evaporate Water-type moves. However, if the team wants then the Nether can just always have Desolate Land weather.
Perhaps the Drowned World could be set to always essentually have heavy rain, the weather created by Primal Kyogre's ability Primordial Sea. The whole place is underwater; there shouldn't really be any Fire-type moves used. Drowned Rapidash probably wouldn't like that though.