Apple Watch is too hot

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Genius Bar Reservation and Apple Support Options - Apple

It is difficult to determine what too hot means from a post, but from the description diagnostics should at least be performed by Apple. You may be able to get remote diagnostics over the phone, but again it would be difficult to assess a "too hot" condition.

Contact Apple Support - Apple Support

Don't charge/use it until you can get it inspected.

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We want to make sure you reach the right team for help with your device. We recommend that you contact Apple Support directly. Depending on your region, you may be able to reach them here: Get Support.

It is always an option but fortunately it is rare. Turn it off to be more sure