I want to add modifiers to my archery mod for accuracy.

I looked over the weather functions but I am not getting how this all works.

How would I dynamically (in a script) get the wind speed, rain fall level and snow fall level that is currently around the player?

No clue about what SKSE might open up for you. However, you may find http://www.creationkit.com/GetClassification_-_Weather to be of use.

It would tell you if the current weather is snow, rainy, etc. I don't think you could find the specific wind speed, especially since it comes is gusts, if it's even measured in any capacity. SKSE may have some relevant stuff, but otherwise the best you could manage I think is to change depending on clear, cloudy (A bit windy?), rain (more windy?) or snow (more windy?).

As far as I know, there are no functions related to rain amounts, the only wind related functions are SKSE functions, and they merely give you the direction.

You could implement specific changes on a per-weather basis as an alternative. However, that will obviously not support custom weather types added by other mods, and would be a pain to implement. AJV's solution is way more convenient to script, but probably a bit less accurate.

ok, right, but HOW is is used? Looking at that I saw it needed a form:

if SomeWeather.GetClassification() == 1

how do I get the current weather form (SomeWeather) from around the player?

Thanks.

I think http://www.creationkit.com/GetCurrentWeather_-_Weather would help you here.