Extra water?!! If your weather is anything like ours, that won't be a problem!
On GW last Friday. Monty said there wasn't much need for water until the plants are in flower. I grow Charlotte (second earlies) which are usually just about ready by now, but they're very slow this year. Their flowers often fall off soon after aqppearing, but by then the potatoes are well formed. This year there are only a couple with flowers on so far. I'm hoping that the last week of rain will be plumping them up now.