Hi to all nice developers!
It would be appealing to have in Gimp scripts or python plug-ins to apply weather conditions to a photo:
1 - rain simulation
2 - snow simulation
3 - hail simulation
There are here and there examples of those, but I didn't find good ones in Gimp, maybe because of my ignorance about them.
Should someone know or be willing of creating them,

Thanks!

Thanks, Graechan!
I have the animated versions under menu Video (rain, fire,..), I just forgot to indicate I like static results. Yes, I can just keep one or two layers as static; so, for the rain, if nothing comes out better, I can use this...

From Fenceposte you should find also a script for animated snow (and fire too )



That is not a limitation : to get static result you may use any "animation" script, just taking care to set the numbers of frames to 1

I believe most of other weather effect will be delusive on static images, things as fog, haze , etc often looks better in animated sequences :
A descending fog may look very suggestive in a sequence, but the single frames if looked separately may looks as poor photos

Many thanks, PC!
Both for the indication about fence-post as well as your comments on static photo "manipulation".
For the snow (an maybe for hail) I was considering something like the old old old plug-ins (for PS and other SW) of Van der Lee: his "snowscape" was also trying to simulate already fallen snow (with not excellent results, indeed...); I was wondering whether someone is willing to try something similar (better...) for Gimp, it's a real challenge.
Also for a raining day is it possible to "complicate" the "simple" falling rain (by adding puddles, lightning, drops, splashes...) ... who knows?

add lighting is simple, you have just to found a good photo with lighting on a very dark sky (on flickr you may found many reusable), and from there crop away whatever is not black sky and the ligthing

once you have it just paste on top of layerstack in Lighten Only mode, so the very dark or black sky will become invisible and only the lighting will contribute to the visible