I wear knickers or shorts/knee warmers up to about 65 degrees. Pretty much for the temperature spread you describe. I can stand having my legs a little sweaty more than being too hot on the top half of my body.
My tolerance for riding in cold is much, much better than it used to be. I heat up very quickly and have to be very thoughtful about how I dress in the spring and fall. So, I wear light weight long sleeved jerseys with a sleeveless base layer and a vest if it's not going to be above 60. Over 60, I will do arm warmers and a short sleeved jersey and vest, with the knowledge that I can take the vest and arm warmers off, if I overheat and still have room to store them, an issue on my road bike.
Last week I did a ride near, but not on the shoreline. It was 50 at the start, and about 40 when I left my house. I was in a real dilemma, as I was not sure how much of the ride would be right by the ocean, with the ever present wind. So, I took my vest and jacket, and wore a very light weight wool long sleeved jersey. When I got to the start, I was freezing. So, I put the jacket on. Wrong move, because after the first 7-8 miles, it got up to about 64. But, I unzipped my jersey and switched out my full fingered gloves for regular ones. That, combined with the fact we rode through some very shaded areas, kept me cool.