depends how much rain you get. I live in the tropics and for most of the year, I don't have to water at all..right now I'm using one gallon pots and when I fert them, I feel like I'm overwatering because of all the rain.
you will likely need to water every 5 days unless your get a terrential downpour for about an hour. even then, lots of the rain hits the leafs and doesn't really make it to the bucket.
from my experience so far this year.... no. got a lot of rain a while back, but as sooon as it went dry, so did my pots, oh well, i can check them (and enjoy doing so) every couple of days.
oh... i also put some rocks on top of the soil in my pots earlier today to help keep the soil moist.