Having the current weather conditions show on your watch is nice, but how do you know that they're actually… you know… current? Here's one way to quickly indicate that, without taking up a lot of space.
Tint: (({dh24}*60)+{dm})-((string.sub('{wlu}',1,2)*60)+(string.sub('{wlu}',4,5)))<5 and 'ffff00' or 'ffffff'
The obvious way to display the last update time is to simply use the {wlu} tag, but that takes up a lot of real estate, and doesn't always fit the theme of your watch. A simple way to indicate that the weather isn't current is to change the color of one of the displayed items. I like to use the “Current Temperature” display, since that's probably what you care most about, but it can really be any item.
Simply change the tint value of that item with the formula above. What that does is convert both the current 24-hour time and the {wlu} time to the number of elapsed minutes in the current day. Then, it simply subtracts the {wlu} total from the time total. This gives you the number of elapsed minutes since the last update. If that's less than 5, the current temperature display turns yellow. Otherwise, it's white.
This is best used with a tap action to update weather, since it can take a few seconds to actually update, and the color change will indicate when that has happened.
Now, there is a slight problem with this formula, since it can't cross midnight. In other words, if weather updates at 23:59, but it's currently 00:01, it will not indicate as current. But, that's a minor quibble. It could be fixed, but it'd mean testing for date as well which would complicate the formula considerably for such a small gain, especially since a quick “update weather” tap action immediately resolves the issue.
The above works well when the Settings:Time:Override 12 / 24 Hour setting is set to “No override”. Changing the example somewhat however results in it working when in 12 or 24 hour format.
Tint: ((({dtp}>.5 and ({dh24}<12 and {dh24}+12 or {dh24}) or {dh24})*60)+{dm})-((string.sub('{wlu}',1,2)*60)+(string.sub('{wlu}',4,5)))<5 and 'ffffff' or 'ffff00'
{dh24} is relative to the Time Override setting and displays as 12 or 24 based on that setting. {dtp} represents the day as a percentage of 24 hours (% 24 hours) regardless of that setting and can therefore be used in determining if past midday. Then by either leaving {dh24} as is if in 24 hour mode or offsetting it by 12 if in 12 hour mode the elapsed minutes are correctly obtained.