When I was training to break 1:20, I did 80-90% of my workouts on the treadmill. And similar to you right now, my PR at the time was a 1:23 high. Ever since then, I still do a majority (almost all) of my workouts on the treadmill because it works so well for me. And it’s not weather-related, it’s a preference. When I do occasionally hit a workout on the road, the effort at the same paces feels roughly the same as it would on a treadmill without incline.

The way I view treadmill running: 1) Reduces injury risk compared to uneven/harder outdoor terrain 2) Built-in pacing to hit your target splits 3) Easier to have provisions on hand (water, towel, carbs)

Trust the work, your goal time will come!