"During the summer, various environmental assaults — including heat, sweating, sunburns, exposure to certain chemicals in sunscreens, swimming, etc. — can actually make the skin more dry and sensitive, and diminish the healthy protective moisture barrier, so maintaining a comprehensive skin-care routine is essential.
I recommend looking for products that are oil-free and non-comedogenic, since heat, sweating, and sunscreen can lead to clogged pores and breakouts, while sun exposure itself can cause the skin to dry out, so it's really important to use the right cleansers and moisturisers in the warmer weather.
I, along with most dermatologists, recommend washing your face twice daily, both morning and evening. Try the Neutrogena Ultra Gentle Daily Foaming Facial Cleanser ($8)."