In July, around 2,500 people telephoned the helpline to report their pet missing, some 800 more than the same time last year, said Swiss news agency ATS.
A further 2,000 people called the centre in June.
In periods of very hot weather pets often search for shady spots and are willing to wander further from their usual haunts to find them, STMZ said in a statement.
Disappearing cats were the case in 85 percent of calls, while other missing pets included dogs, tortoises, birds and rodents.
Founded in 2001, STMZ is a national data platform recording the disappearance of domestic animals.
Maintained by 25,000 volunteers, it is supported by Swiss Animal Protection (PSA), the Society of Swiss Vets (SVS) and the Animal Identity Service (ANIS).
A principal function of the organization is to allow people with missing pets to post a notice on its website, free of charge.
In 40 percent of cases, cats return to their owners of their own accord, according to STMZ.