watchOS 4.2.2 (build 15S5534a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2017-12-19T18:05:58Z. The update package is 64.64 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 90c5b172521b68ec0016f9e995f2d63e6dd36955.zip.