Yes, mortgage rates can move noticeably inside a single day. They ride the bond market, specifically mortgage-backed securities, and that market reprices in real time. The usual movers are economic data and Fed signals. A jobs report that comes in much stronger than expected, or a CPI inflation reading that runs hotter than forecast, tends to push rates up, because both suggest the economy is running warm and the Fed may stay restrictive. Softer data tends to pull rates down. Occasionally a move gets exaggerated by a technicality, like a rounding quirk that makes a report look worse on paper than the underlying data really was. Not every wiggle is real, though. On thin trading days (holidays, half sessions), low volume can produce odd swings with no news behind them, and those usually never reach the rates lenders actually offer unless they persist into the next full trading day. Experienced capital-markets desks recognize thin-volume noise for what it is. If you want to follow along, MBS Highway and MBS Live both track the bond market intraday, and the Mortgage News Daily rate table right here on our site shows where the daily averages sit. For you, the number that counts is the rate you can actually lock on the day you are under contract, and when you get close, we watch the market alongside you and help time the lock.