Air in my system

After having my pool for three weeks now with no problems. Out of the blue today my pressure went down and I could see lots of bubbles inside the glass on my pump filter basket. I turned off the pump and open the air vent on top of my filter to let out the air out. Turn on the pump and everything was back to normal. What caused the air to get in my system? The only thing I noticed is that we had a lot of rain today and my pool was almost to the top of my skimmer (I keep it about half way up). Could the hard rain some how caused air to get in? It had stopped raining for about 2 hours be for this happen. I would think if I had a major problem once I let the air out and turn it back on I would still have a problem. The pump has now been running for over three hours since this happen and still everything is normal. I am new with this in ground pool stuff and was wondering if I had some kind of problem.
Please help!
Thank you!

I am getting air in my system too and waiting on a foot-dragging solar installer to repair what I think is the problem (I have 2 months left on their warranty). I have to open the air vent with the filter running to bleed out the air. Why do you turn yours off first? That part doesn't make sense to me. You are introducing air into your filter and plumbing if you turn off the pump first.

The only reason I turned off the pump before letting the air out is because I didn’t know what was wrong at the time. Anyone have any idea what happen???

Reno,
My best guess is that you got a vortex flow in the skimmer and it sucked air. Sometimes, even at high water levels, when the conditions are right, this can happen. Skimmers are designed with various types of weirs (sp) to prevent this. Some have a door type mechanism, others a floating thing, or something else.
Al

I'm always reading threads to find out if my problem might already be answered by someone else's problem. That's why I'm tailing onto this one. I've got foam on the surface of my pool and it looks like there are bubbles in the filter. I've never heard of opening the filter, but it sounds like that worked here - is it the hole at the top (I have a Jacuzzi - ST24). Does it open easily and should you keep the pump running?