Set up rain barrels now, rather than waiting. I have two under the downspouts in the back yard, totaling about 120 gallons. One good t-storm and they are full. I use the water for the veggies during the summer. I do consider these part of my emergency supply. I would not drink the water without taking normal purification precautions. Even with screens on top there is dirt/debris in the water, plus algae growth and who knows what else.