If you’ve noticed, there are 3 important variables included in the mod settings:
metar_polling_frequency_minutes: This, I think, is self-explanatory. The value (in minutes) determines how often the mod pulls the METAR report from the AVWX server, using the plane’s current location (lat and long) as the arguments. The server returns the current (or sometimes, cached) report from a monitoring station that happens to be the closest to that position. 3 minutes seems like a good number, unless you’re piloting a super-fast airliner, in which case you may want to reduce it to, say, 1 or 2 minutes. Be careful, though, as pounding the server with extra requests is an overkill, as you will be getting lots of duplicate METAR reports with no real benefit to you. Also, keep in mind that with the free “Hobby” tier you’re limited to 4000 reports per day.
weather_transition_span_seconds: When a new METAR report is received and it is differenrt from that last one, the mod generates a new weather snapshot and then starts a “transition period”: it interpolates all values between the current and the new weather snapshots and applies the changes to the in-game weather in small steps. That’s when you start seeing your cloud layers move up and down, change their shape, the rain die or pick up, etc. This particular variable controls how long such transition periods last, in seconds. Set this value too low and the changes are going to be more abrupt. If you increase the value instead, the transitions will last longer. I’d suggest you experiment and pick a value that is closer to your preference.
weather_transition_step_seconds: This value controls how smooth the weather transitions are (see above), i.e. it dictates the duration of each small step at which the incremental changes are applied to the in-game weather. I left it at 0.5 seconds in order to accommodate those folks who have weaker PCs, but you may want to reduce it to 0.1 sec or even lower, if you have powerful hardware. Pay attention to your effective frame rate, though: for example, if your sim runs at solid 60 FPS, then there is absolutely no reason to set this value lower than 1/60 sec, i.e. 0.0167 sec. Even that would be too low, as each adjustment to the in-game weather values may cause MSFS to stutter slightly and you may do more harm than good in such case. Values that cover a few frames like 0.1 sec or slightly lower seems like a good pick. Again, experiment and see what works best for you.
Now comes a valid question: What if the weather is currenly in transition, but yet another, differerent METAR report is received? This can happen when moving very fast over a few airports or stations in sequence. In that case, the mod abandons the current transition, picks up where it left off and starts a new transition, this time to that new METAR report. This may lead to what might seem like a prolonged transition period. No need to be alarmed. (Note that this would only happen if your weather transition period is longer than your METAR polling interval. By default, they equal: 3 min and 165 sec respectively.)
The last note: If you change any of the above settings, you will need to completely restart the sim. It will not pick up any changes made to the JS file after the sim had loaded it in the beginning.