The USDC always adapts to the dollar exchange rate. If you purchased it with American dollars, the value will stay more or less the same. That is the stable part in why it is called a stablecoin.
That being said, the value of the US dollar itself does fluctuate. So if you made your purchase with a different fiat like the Canadian dollar or another cryptocurrency, there could be some fluctuation in terms of value – though the ups and downs will be far less than what has traditionally been seen with digital coins like BTC.