Slightly, yes — follicles run roughly ten to fifteen percent quicker in warm months. The catch is arithmetic: hair grows about a centimetre a month, so a summer bonus is a millimetre or two. You will never see it.
Transcript
Hair grows faster in summer. This one is actually true. Follicles run a little quicker in warm months, roughly 10 to 15%. The catch is arithmetic. Hair grows about a centimeter a month, so a summer bonus is a millimeter or two. You will never see it. What you notice in summer is humidity swelling each strand, which makes hair look fuller, not longer.
What you do notice in summer is humidity swelling each strand, which makes hair look fuller rather than longer. That is a texture effect, not growth.