B.R.
I'd try to get him up now... and in the future start getting him back on a better bedtime routine.
Also, you mention not being able to let him get his energy out due to the rain. Put on some lively music and start dancing with him. Keep that going for about half an hour, and repeat the process several times today. Not only will your little one get his energy out, but if you are dancing with him, you'll get some great exercise for yourself.... a 'win-win' situation!