After my earlier post about weather, reader Tyler Durden mentioned having created a tool that generates climate-appropriate weather for campaign worlds, including their effects on travel times. He was kind enough to offer to share it (and also translate it from Italian for the Anglophone readership) and you can find the link here.
There's a readme file with the tool, which covers how to use it; you really want to play around with it a bit to make sense of it, though. I do a fair bit of work in Excel myself, so I have some idea of the enormous effort that's gone into making this.
Okay, who's this good for? Primarily I'd say it's useful if you're doing games based on a fairly concrete map (either traditional hex-based, or just with a good sense of how places relate and their terrain type), and would like to include weather that doesn't depend on the GM's imagination and grasp of meteorology. This tool is neutral and systematic, but should produce consistent and believable weather. If your group doesn't want to be dependent on GMs making decisions, it should be an asset. It's not just about the weather; a map-based campaign typically involves a lot of travelling, and knowing how weather conditions will affect travel and hazards is a big help. Sandboxy old-school campaigns ought to like this.
More broadly, it should also be helpful to any game that wants to include weather for a touch of realism, helping to give a sense of place; this will be particularly the case if your game skips around between mountain, forest and seaside. Even if you'd prefer not to model travel in detail, you could use the tool's calculations to inform descriptions and narration. It might also throw in unexpected twists that inspire new opportunities - seeking shelter from a rainstorm, say, or needing extra water during an unseasonal heatwave.
Actually, this would also be a great asset to budding fantasy authors who want to feature the classic travelogue segments. No more worrying about plot holes and inconsistencies, just use the obligatory front-inside-cover map with this tool to calculate all your journeys!
I've only really had time to tinker with it a bit so far, but hope it will be useful to others who might read the blog and appreciate Tyler's hard work.