Thank you! I don't think it's perception. I cannot see hwy or train track. In summer, I actually forget about train track. It's between house and hwy. In winter I hear hwy traffic, train and whistle occasionally (like this morning).The same here. I don't know if it's because of the bare trees/ lack of insulation or just my perception. In the winter I can occasionally glimpse trucks along the highway. When the trees are full, I don't see them so "out of sight, out of mind" thing going on?
Here's an article on sound differences in cold weather
https://www.discovery.com/science/Sound-Carries-Farther-Cold-Days#:~:text=Because sound moves faster in,travel farther in chilly weather.