Even with a wether checker there's still no clear "indication" of light weather so it's not like a weather checker npc would help lol. Both fire/light lack a true indicator from an npc as to if they'll be that type of weather so a better suggestion I would think is if they added a hint at "heatwaves" and "aurorastorms" if there are chances at those weathers during that hour.

I've mentioned this in another topic but why not revitalize MMM by adding weather runes that could augment the zone with a certain weather trype or perhaps it puts the party under a "weather effect" that works for trials. Basically could be like:
-Rune 120 "Heatwave" -Augments players and foes with fire weather-

Then with use of other runes you would be able to augment it in a way to get the mobs you want to a certain extent though some mobs would still be out of the loop. But for trials that focus on an family of mobs like any beast or lizards, it would mak'em easier to go through with an MMM or two.