Winter Potty Recommendations?

We have the sweetest 8 month old puppy who suddenly this winter (we’re in the Northeast) has been refusing to go to the bathroom for extremely long periods of time (to the point that I’m worried he could develop a UTI!). This morning after being in his crate for nearly 10 hours for bedtime, it took 40 minutes of me walking him and then standing in my backyard to get him to pee. He didn’t go #2 until about an hour later (we went inside between). Tonight I was out for another 20 minutes in our backyard, which is his normal spot, then wandering around to his other spots in the neighborhood and he just never went. So now he’s held it since his 5:30 walk and is in bed … I have no idea what to do! We have tried upping the potty treats and doing big celebrations but that doesn’t seem to be enough motivation anymore.

Has anyone else experienced this before? We’ve only had dogs who are raring to go potty the second we get outside, so this is new for us — even in the warm weather he was never an immediate potty boy, but it was definitely not this bad!