It depends on the school. Some actually have rec due dates several days after application. Others provide a little leeway, especially if you call. I forget who but someone had a person with a late rec for MIT. Normally MIT requires recs ontime but he called and talked to them and they were willing to accept it.
that was me.........Yes you can talk to them...but make sure that your recommender at least started the process. That was the main reason mine was accepted.
FYI, my reco came in 48 hrs after the deadline, but the app was still accepted.
Alternatively, you can call the school tomorrow and let them know that your recommender was caught up with something unexpected and thus the letter will be delayed