MacRumors published a story that Apple has released the second beta of watchOS 10.3 to registered developers.
Apple Seeds Second Beta of watchOS 10.3 to Developers
Apple today seeded the second beta of an upcoming watchOS 10.3 update to developers for testing purposes, with the beta coming three weeks after the release of the first watchPS 10.3 beta.
To install the watchOS 10.3 update, developers will need to open the Apple Watch app, go to the Software Update section under "General" in Settings, and toggle on the watchOS 10 Developer Beta. An Apple ID linked to a developer account is required.