Weather at any given time and place on the ST is a matter of probabilities, though some themes tend to dominate the mix. I would go to one of those weather web sites and look up average weather conditions for certain regions at specific times of the year. Even then there are no guarantees. Go through Van Horn, Texas in February one year and it may be sunny, cloudy and in the fifties and sixties. Go through Van Horn in February the next year, and you may find yourself snowed in for six consecutive days. I crossed the US on the ST one year, and had an hour of rain in the entire two months. Another crossing on the ST had me inside drinkng coffee for hours at a time, day after day, waiting for the rain to stop. In February, March, and April be sure to bring cold weather clothing.
I am heading west on the ST tomorrow morning unless it is raining like this morning. I expect cold weather definitely. Here in Florida it's warm, but I am not letting that fool me. I am very well aware of what I am up against. I am starting well south of Saint Augustine. I will not be seeing that city.