I'm having similar issues with my S3 after the latest update. The battery drains rapidly. Possibly a memory leak issue. I also noticed that the weather app had an update today.
Same version as yours, I have disabled power optimisation. I took my watch off the charger 14 minutes ago and Samsung gear is telling me it's used 34% of battery since last charged.
Watch is still at an indicated SOC of 100%, so I assume that 34% is 34% of 0.5% of battery discharge since putting it on 18 mins and 44 seconds ago.
If you updated your Gear S3 I really suggest wiping it, clearing the bluetooth connection from your phone, clearing the samsung health app storage cache and program data and un-install it as well as the Gear app.
Start over from scratch, it really doesn't take very long.
After you finish and start over from scratch, make sure you get all the notifications turned off you don't need like sitting still alerts, leaving on the important ones like phone calls, texts, emails and then turn off all the monitors in samsung health, heart rate, running, biking etc... Turn off the wifi, turn the sound volume down a bit, turn the brightness down as well (you can easily go down half way and it is still plenty bright). I also turn off the wake on wrist movement and wake on bezel movement and turn off the SVoice listen. I activate SVoice with the bottom button on the watch "press twice". I use SVoice a lot. I like starting with everything turned off to see how it performs and then go from there.
This watch in stock form out of the box connecting to Galaxy S7 edge phone and not adjusting any settings gets you about 3 days use "turning it off at night" with the original software that came on the watch. I have a feeling with the updated software it would be even worse. You can drastically improve battery life going through the settings and making adjustments like I mention above and make the watch a lot better in my opinion.