Since it hasn't happened under similar circumstances before, it may well be a clog or obstruction in the drainage system. If you know where your drainage system runs to daylight (assuming it does), check the outlet pipe. It may be as simple as debris or sediment build-up in the end of the pipe. If you can't see any obstruction, or the system empties into a sewer, infiltration basin, etc., you may need to have a plumber or sewer/septic contractor come take a look. Find someone who can run a camera up the drain outlet and/or down the floor drain and inspect for blockages. Many such contractors can do at least a temporary repair without needing to dig anything up. Unfortunately this is one of those things that might be no big deal or might be more serious. Either way, good luck!

We haven't made any changes. Our house sits on a little rise with sloping away form the house. We have never had any visible water close to the house.

Most likely it's the water table, this things unpredictable and after a few days of rain it became elevated.

Sounds like you have a french drain in your basement, one thing you can do is install a drain system around perimeter and tie it into the sump-pump pits... but before you do that, make sure your perimeter grade has a slope and is pitched away from the foundation and also check your gutters make sure they clean and there is no overflow and leaders are extended far enough to discharge the water away from the foundation.