I am planning to install hardwood floors, but I heard the floors get cupped in humid conditions. Is this true

High Humidity Levels
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If the humidity hits above 55%, you're opening up a chance for moisture to seep into the wood. Too much moisture and the floor boards could begin to swell. This swelling can create pressure between the boards, which can cause the boards to warp or cup. This is true for both solid hardwoods and engineered hardwoods. Remember, while engineered hardwoods tend to be more stable than solid hardwoods, they are still susceptible to moisture.
Low Humidity Levels
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While high moisture levels can damage your floor, it's not the only thing to watch out for. If the humidity level drops below 35%, low moisture levels can also be a problem. Low levels can cause the wood to dry out, which, in turn, could weaken the wood, causing the floor to splinter. It could also lead the floor to “check”, meaning that it could split along the grain. This can also damage the finish, which would become an issue during your regular maintenance. "

From: The Tale of Hardwood Floors & Humidity » Armstrong's The Floor Board Blog