Plant potatoes in April/May. It takes 90 to 150 days for them to mature.
You may want to contact your local Extension Service for specific info.

You are a little further north than I but I can't Imagine planting potatoes in April/May unless your talking sweet potatoes. The heat would kill them by July and they would not set anything worth digging. Potatoes are a cool season plant. Check you local extension office. My guess is late Feb. early March. I plant early to mid Feb. here in midlands area of SC. with Harvest in May for early varieties and June for late. I have not had succes growing in the fall. The tubers will not sprout. I was told to chill them but still nothing. I did have potatoes come up the following march in the area I tried to plant fall potatoes.

I've not had a problem with putting out a few potato eyes (or composted potatoes) in early August, despite the "rules". They sit and sulk until the weather cools, then produce for a short or long while depending on the fall temps.

I wouldn't rely on them for my main crop, but grabbling for new potatoes in the cool fall air is a treat.

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Planting potatoes in August is a common practice here in South Louisiana (8b/9a). Give them a little protection and go for it.