Frizzy hair

I have medium length wavy brown hair. I get it colored 4x/year, adding highlights. The top layer is completely frizzy and straight, while the hair underneath is healthy and wavy/curly. This is all fine when I’m curling or straightening my hair, but in the summertime I don’t “do” my hair as often, since the humidity destroys any style. My hairdresser says it’s just my age. I’m sure it’s the chemical processing, but I’m not willing to go grey. Are there any products you’ve found to help with the frizziness of the top layer?