Rain or no rain, you've got to get some chlorine in that pool or it is going to turn a beautiful shade of green right before your eyes! Also, add some Borax to get your pH up some. Add a half a box, let it circulate a couple of hours, then retest and redose as needed to get it somewhere 7.2-7.8 with 7.4-7.6 being best. You need to do this before your pH drops below 7.0 as readings below that are acidic and can damage a pool.