I’m using $wf(max, 0)$ and $wf(min, 0)$. They are accurate in the preview on the phone, but never automatically refresh on the watch. Will only refresh if I click the sync KWCH editor to watch icon.
For current temp I use a complication which always works.
I believe currently automatic syncing of data with the Watch app is not implemented in v3.74. I have read somewhere that it is on the feature list for 3.75 release.