The following steps may help, having resolved issues with the Weather app and Weather complication for other users.
If you have not yet done so, update your iPhone and Apple Watch to the latest compatible software versions, starting with your iPhone:
On your iPhone, in the Watch app, go to: My Watch (tab) > Weather > Default City > choose Current Location (or a specific location from those that have been added to the Weather app on your iPhone, if preferred).
On your iPhone, go to: Settings > Privacy > Location Services:
At the bottom, tap on System Services > check that Setting Time Zone is enabled (you may also wish to enable all other system services, if they are not presently enabled).
- Check that Location Services is enabled.
- If the setting is already turned on, try turning it off, pausing for a few moments and then re-enabling it.
- Check that Apple Watch Faces is set to While Using.
- Toggling the setting to Never and back again may help.
- Check that Weather is set to Always
- Toggling the setting may help.
Check that Bluetooth and Wi-Fi are both enabled on your iPhone:
- iPhone: Settings > Bluetooth - on.
- iPhone: Settings > Wi-Fi - on.
- For the best performance from your watch, keep both Bluetooth and Wi-Fi permanently enabled on your iPhone.
On your iPhone, go to: Settings > General > Background App Refresh:
- Check that Background App Refresh is enabled.
- It may also help to enable the setting for Weather.
On your iPhone, in the Watch app, go to: My Watch > Complications:
- If you are currently using a third-party weather app (such as Yahoo Weather) for your watch face complications, try removing it (via Edit, upper-right) and using Apple's built-in Weather app instead.
Restart (normally) both your iPhone and your Apple Watch, turning both devices off together, then restarting your iPhone first:
If the issue persists, unpair and re-pair your Apple Watch: