I understand your concern Heinz although mildly optimistic it won't be an issue. The units are heavy as the whole rear of lamp is a finned cast aluminium heat sink. The suppliers mention that light output may be impaired if they run too hot, that's all. Working temperature is -40 to 60°C. Others I've seen claim higher.
I have a laser thermometer so will try and obtain some accurate temp indications. The bowls are plastic though so not going to conduct much heat. If it becomes an issue I would drill a hole in the base of bowl with rubber tube inserted externally to prevent direct water ingress whilst improving air flow.
