Can rain make pH rise?

Luckily we don't get a lot of Rain in Las Vegas, however it does seem that after each rain my pH rises, any connection?

Generally, rain may make your pH go down--acid rain. If it's going up it may be either coincidence or somehow, the rain is causing the pool to aerate--and that pushes up pH.
Other possibilities: If you are chlorinating with cal-hypo and covering the pool when it's raining, the cal-hypo could be pushing pH up.

I'm just guessing here......................