Our female whippet is almost one and a half. She is out side most of the day whilst we at work. She loves her bed and blanket and sleeps in the laundry at night since she was a pup. For a good year almost she hasn't weed in there during night as we always make sure we watch her do one outside before bed. Lately she has weed in there a big one on floor? Why? My only thought of different factor is it may be getting cooler from winter in there but she sleep under blanket? Help?

Could be a bladder problem (I know, foregone conclusion) but if she is l.5, her bladder hasn't caught up to her growing body yet so this may not be the issue you are thinking of. Her bladder will catch up to her proper size soon. Just do due diligence and get her out for another pee. Good little dogs these whippets, pretty smart and very clean.