When the weather starts to get hot and sticky, we often don't feel like adding moisture to our skin. This is a mistake. Heat and sun can zap essential hydration and oils from your skin, so you have to be sure to add oils and water back into your dehydrated skin during the Summer months. Also, if your skin is used to that supple moisturizer each day and suddenly doesn't have it, it'll go into dehydration mode. Your skin will start to overproduce oil to make up for it, and then your already oily skin will get worse. If your regular moisturizer is feeling too heavy for the hotter months, switch to a lighter, more Summer-friendly formula, such as an oil-free gel.
My summertime favorite is Clinique Moisture Surge. This lightweight, oil-free gel is made up mostly of aloe and water, and it provides hydration without feeling sticky or greasy.