I just returned from Wanderlust in Vermont, which was a four-day yoga and music festival, and I really had a blast taking yoga classes from luminaries like Seane Corn and Cyndi Lee, hiking part of the Long Trail, eating lots of great healthy food and learning new things like hooping and stand-up paddle boarding.
Like any summer festival, I packed for this one carefully, anticipating plenty of changing to keep cool and comfortable (not to mention clean and less smelly). Here's my list of must-haves for any warm weather fest, whether it be focused on yoga, music, food or any combination of the above.
A great hat: You need to keep out of the sun, to protect your skin from the sun, keep cool, and maybe even to keep rain from blinding you if you get caught in a rainstorm. (Hey, it's summer; anything could happen!)
Two water bottles: It's always best to have backup! In the case of festivals, be aware that you may not be able to bring or carry glass water bottles in, so bring in some stainless steel bottles. And I suggest bringing two because that way you can keep one in the fridge so you always have cold water available.
Layers, layers and more layers: I like to imagine each layer I wear as its own outfit. So I brought my Lululemon Open Mind bra, which is cute and comfortable enough to wear as a solo top layer when it's hot, but also works as a base layer too. Over that goes a light tank top or T-shirt (or dress) and I always keep a light sweater or jacket (if rain is anticipated) in my backpack. I also carry a large scarf, which can be sat upon, draped over the shoulders, wrapped around the neck, or used as a dress if my clothes get soaked or filthy for some reason. If possible, wear a good pair of shoes and carry a pair of flip flops so you don't have to walk around with wet feet if you land in a puddle. Layering a hat and sunglasses will keep the sun off your face and shoulders in various combinations. Wearing a pair of shorts under a dress makes a more feminine outfit more comfortable (for sitting on the ground and such) and also means you can pull the dress off and just wear the shorts and top solo when it gets steamy (or if you find a place to take an impromptu swim).
Simple accessories: Even when I'm running around outside all day, I still like to wear something stylish and fun. My favorite way to achieve this is with medium-sized bracelet cuffs, or a collection of slim bangle bracelets. They are light, fun, and can be removed easily if you are doing yoga or another activity, but usually don't get in the way. A colorful scarf can also add plenty of interest and a shot of fun to any ensemble.
A great go-to hairstyle: I get really bored keeping my medium-long hair in a ponytail, but mostly I want to keep it off my face and neck (and since my hair is naturally very curly, it can get crazy-frizzy if left to its own devices in the summer humidity). I like to pile it on top of my head in slightly-over-the-top buns, sometimes using colorful clips and pins to keep it in place. Braids are also a fun way to keep hair away — this year the "Heidi braid" hairdo is popular, and couldn't be easier (see this instructional how-to).