Forecast: Warm
A sleek hairstyle like Beyoncé's is stunning—but won't always survive the great outdoors. To avoid looking like a sweaty, frizzy mess, save this 'do for a day when it's comfortably warm with a slight breeze and no chance of rain.
Forecast: Warm
Unless the heat is stifling—which it isn't—you should embrace your tresses! Save the high-bun for steamier temps and try a sexy yet practical half-updo like Jessica Alba's for an evening out (Alba wore the style to a recent dinner party).
Forecast: Warm
Blake Lively's cascading locks are hot in more ways than one. If you have a thick mane too, push it to the side and let your neck breathe. Throw in some fishtail braids and you're red-carpet ready!
Forecast: Warm
Beach waves are always en vogue for summer—and the more texture they have, the better (so if frizz strikes, don't fret). Nicole Richie pulls off the trend perfectly.
Forecast: Hot
Straight, bluntly cut bangs are in, but sweaty bangs aren't. To avoid the stuck-to-the-forehead look, opt for sparse fringe like Zoë Kravitz's.
Forecast: Hot
Full, well-groomed brows are in for summer and fall; model Jessica Stam shows hers off—and keeps her forehead cool—with a well-placed plait.
Forecast: Hot
Are you obsessed with short hair—but not ready to part with your tresses? Lighten up (literally). You can still make the cut with a long asymmetrical bob like Jennifer Aniston's.
Forecast: Hot
Mila Kunis knows about hairstyles with benefits! A low chignon with face-framing strands is sophisticated, but also practical and fuss-free.
Forecast: Boiling
In the midst of a heat wave? Take it off! Alexa Chung proves a short chin-length bob can be superstylish. The best part: If you go for a textured, delightfully untamed look like hers, you can relinquish control of your tresses.
Forecast: Boiling
Is stepping outside your air-conditioned home like entering the Wild West? Do as Cowboys & Aliens actress Olivia Wilde did, and go for a high-pony. Incorporating volume at the crown catapults the look from the gym to the red carpet.
Forecast: Boiling
Whitney Port takes her high-pony a step further and turns it into a bun. A few bobby pins, and you can be ballet-chic too!
Forecast: Boiling
Unfortunately, when the weather is painfully muggy, there's no magic wand to wave it away. But a pixie like Emma Watson's—or a tube of hair gel—can seriously improve matters.
