As it happens in my playgroup, there is a very decent chance one of the players asks a question like this: What time it is? What's the weather like? What's the result of my Read Weather spell? What is the lunar phase this night?
Some of these questions might be friendly poking, but some of them are valid during the campaign. When unprepared, you can just make up the time /quite easily/,but coming up with weather patterns is about as fun as it sounds and don't think about screwing up with full moon just after announcing waning moon.
Soon I am about to start a Carrion Crown campaign. If you read the campaign, you might be familiar with S-man and his shenanigans, lunar phases might be a thing when the Broken Moon comes up, basically most of the adventure the party is moving outdoors from one county to another.
Yes, there are random tables weather or whatnot, but rolling bunch of dices in front of my player doesn't sound a lot like fun.
So I recently came up with this idea. To make things easier, I would make a weather chart, based on the historical weather archives. I could fill in all sorts of things, like above mentioned lunar phases, festivals and holidays, actions, that I know will come up (like the S-man)...
The question is, has anyone tried something like that? What sorts of information did you use? How well did it go? Was it well received by the players? Or is it something that is just a waste of time?
I did what you are envisioning for a homebrew campaign I ran in the River Kingdoms. I grabbed a Golarion calendar, identified a geographic area I felt closely represented the climate of the River Kingdoms, and looked at historical weather reports to track the weather day by day.
In the end it was a decent amount of work and only provided marginal benefits to the atmosphere of the campaign. I haven't done it again since, as there are more pressing demands on my time as GM and I just felt this much specificity wasn't being worthwhile. My suggestion is to just go with the random weather generator or make it up based on your understanding of the local environment. Good luck!
I have done that for my Crimson Throne campaign, especially for the periods where the party is traveling.
I determined the equivalent climate location in the real world and went to weather underground.
You can select a place, and then look at it's history for any range of time.
It will give you a nice chart/table of the High/Avg/Low temps, humidity, visibility and wind on each day along with the precipitation and any other events (like thunderstorms, snow, blizzard, fog).
Then if you want the moon, you can just add that in yourself.
I actually mark off each day on the sheet as the game progresses, so at any given time I can tell them "it's the equivalent of the end of December" or the like.
I say run with your intuitive storytelling sense to determine weather. Describe the weather in each expo dump so that the players don't have to ask. If someone uses a spell, reward them by giving some information that makes them feel as if that spell slot was worth it. Track the days as they progress throughout the game. Full moons and New Moons are significant as they would affect perception checks, as would overcast skies. Just assume that full moons occur around the beginning of the month, and new moons occur around the middle of the month, no need to be exact. Now that I think about it, the moon affects the tide, if its a full moon, high tide at night, low tide at noon, etc. this could change accessibility, tactics, etc. So, I think it's important info to keep track of, but even if it's treated haphazardly, most players may not even notice.
I use a random weather generator and roll it a month in advance, adding each day's weather into the spreadsheet I use as a calendar (each month is a different table). I think weather is important, as there are a surprising number of traits and other mechanical abilities that only take effect during particular types of weather, and it helps make the setting more "real." Last, it makes for some organically memorable encounters. A battle against ogres is one thing; a battle against ogres in a blizzard is a whole different thing :)