Beach waves are the ultimate Summer hairstyle, but windblown and frizzy are two very separate looks. InStyle spoke with Olivia Wilde's hairstylist to get the must-have product for sleek waves this season.

While bad hair days usually feel like an inevitable part of summer, that certainly wasn't the case for Olivia Wilde at the premiere of her new movie, Third Person, in New York City. The steamy weather didn't stop the star from stepping out in sleek waves — in fact, there wasn't a hint of frizz in sight.

"It's sticky and humid out, so I didn't want her hair to look or feel too heavy or weighed down," her hairstylist, Rebekah Forecast, tells us. "I wanted to give her a style that enhanced her natural wave and looked smooth and effortless." Goal achieved!

To weather-proof your waves at home, Forecast recommends prepping with one to two pumps of Herbal Essences The Sleeker the Butter Smooth & Creamy Hair Milk ($4) through the ends of damp hair to lock out humidity. While blow-drying on low heat, work your hands through your strands as you dry to create natural looking waves like Wilde. Once setting with hairspray, grab two-inch sections of hair and wrap the mid-shafts around the barrel of a 1 1/2-inch curling iron (or alternate between two different sized irons to create more depth). After curling each section, finish by working three to four pumps of Herbal Essences Moroccan Me a Miracle 7-in-1 Serum ($4) through the ends for a boost of shine and added insurance against the heat.

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