Creating Weather At Point

I know there is a trigger to create weather at a region, but is there a trigger to create weather centered at a point with X width and Y length?

Yup. You can do it either using a region centered on the position of something..
Environment - Create at (Rect centered at (Position of (Triggering unit)) with size (32.00, 32.00)) the weather effect Ashenvale Rain (Heavy)

or using coordinates..
Environment - Create at (Rect(0.00, 0.00, 0.00, 0.00)) the weather effect Ashenvale Rain (Heavy)

or using two points (the opposite corners of the region)..
Environment - Create at (Rect(0.00, 0.00, 0.00, 0.00)) the weather effect Ashenvale Rain (Heavy)

I'm aware it says "Rect" in some places, just replace that with "Region", which is what I think the standard editor uses. I use UMSWE, so I have Rects rather than Regions.

Ah. Merci.