I use Kose Medicated Seikisho Whitening Mask not only in Summer but also during the Winter. However, I only apply it to my t-zone area when the humidity is low. It removes my stubborn blackheads to keep my pores clean and I can actually see my blackheads stick to the mask after peeling it off.
I am living in Southwest region where the heat makes me sweaty but at the same time, the dry heat dehydrates my skin in a flash so I use this mask once a week and follow the below steps to maintain my natural skin's moisture:
1) Use lukewarm water to clean my face and "open up" my pores;
2) Apply a thin layer of hydrating toner as a base to protect the skin;
3) Apply Kose Seikisho Whitening Mask for 15-20 minutes or until the mask is dry;
4) Peel off the mask and clean my skin completely using lukewarm water. Then, apply Sekkisei Whitening Lotion and Whitening Emulsion as usual.