thanks for your replies. Going forward I will get Charley back into a his routine so that he knows like clockwork when he will go out. The weather made me get sloppy and I was worried about him getting all sloppy outside.
As you've heard from others, it's not unusual for puppies to go through (sometimes several) periods of regression.
...and the other factor is the weather. We thought it was great that Kodi preferred to go outdoors UNTIL the bad weather hit in his first winter. THEn we were sorry that we hadn't REALLY reinforced the litter box.
Since then (and especially in the fall, as winter approaches, we STILL make a HUGE big deal praising him for using his box. We no longer say anything about him pottying outdoors, since that is already a "preferred" activity. We actually have to be careful about how we handle him pooping in the box, since he likes his privacy. So if we see him hanging around the box, we casually leave the room. But we can still hear him get in the box and circle, sure signs that he is going to poop. When he is just finishing up, we quietly step back in and give him TONS of praise. It's pretty funny, because he gets VERY excited about the ritual of us piking it up and disposing of it in the toilet... He has to accompany us the entire way, bouncing every step!
Another thought I had...I don't know how large Charley is now, but Kodi became very resistant to using the litter box when he became too big to circle in it easily. We replaced it with a larger one (the large sized Rascal Dog) and his resistance went WAY down.
Another thing that caused resistance and accidents was when we (briefly) switched from wood pellets to the commercial "dog litter". I THOUGHT I was cleaning the box regularly. (with the wood pellets, you can see immediately if they've peed in it even once, because the pellets swell up and break apart) But with the commercial litter, when I got down on my knees one day to sweep up pellets that had been kicked out of the box, the ammonia smell was overpowering!!! The commercial litter is much more absorbent, and the urine sinks down through it. You can't see on the surface that the dog has used the box. I switched back to wood pellets, and he started using the box reliably again.
So, I guess my message is, obviously you want to keep accidents to the minimum, because unlearning takes longer than learning. But a single accident isn't the end of the world, and you AREN'T a "bad doggy parent"!
And there can be a number of things that can contribute to accidents, especially with young dogs, whose understanding is tentative. (and Tom says it's ALL habit, with very little understanding for well past the first year) You are probably spot-on with your assessment of the weather contributing to his accident, but I thought I'd mention a few of the other "pitfalls" that caught Kodi and me!