Photochromic lenses and temperature

Photochromic lenses normally darken in response to increasing UV, but
unfortunately do so much less as the temperature goes up. Are some
brands less susceptible to darkening in the cold?

I got some replacement P.L. from the same source, and unlike the
originals they hardly darkened at all on hot days. Then a cold cloudy
(high UV) day made them very dark. I know the common approach is
temperature sensitive due to the physics, but are some formulations
even a little bit less so? tks