No excuses If it doesn't rain/hail/storm at the moment, I go out and don't go far in case of stormy weather.
Yesterday I dressed up and the moment I did, it started to rain. I watched a movie, waited for it to stop and went out. The wind was awful but here on TE I read this clever thing: "Hills make you stron, wind makes you mean" and I liked it very much.
Some motivation of not quitting is making an appointment with a group or friend and the thought of letting them down makes you pack your stuff and go out. And even if the weather becomes sh***y, sharing the storm and rain with another person is not so bad as being alone in the rain. I've experienced this and when the conditions are not great, you're more likely to quit when you are alone.
But still, don't feel guilty, if the weather is bad, find something that you also enjoy, like you did with the walk and the dogs.