Summer can be pretty rough on our hair. So can winter. Spring and fall are relatively gentle <---felt the need to include that just so I could go through all the seasons.
It's a great idea to deep condition your hair at the very least once a month. Depending on your texture, condition, and what your stylist recommends--you can deep condition up to once a week (this may be excessive for most textures, and really is aimed at very processed, dry and brittle hair).
If you have virgin hair (hair that has not been colored), and it's in pretty good condition, I'd recommend deep conditioning about once a month.
If you have gently colored hair, maybe a few highlights or occasionally a demi-permanent gloss, it wouldn't hurt to deep condition at least two times a month.
If you have heavily colored hair, dry or brittle hair, or any texture that is excessively dry (colored or not), I'd recommend deep conditioning 2-3 times a month.
The best time to deep condition is after your hair is freshly washed. Distribute a healthy amount of the deep conditioner all over your hair (avoid your roots if you struggle with a lot of oil production) , and rake through it with your fingers to spread it from roots to tips. If you need it, grab a very wide tooth comb, like this one, to comb the product through your hair. Follow the timing directions on the bottle, although most deep conditioners say to leave it in anywhere from 5-15 minutes.
To maximize the benefits, twist your hair gently into a bun, and secure lightly with a plastic clip. Put on a plastic cap, and if you really want to take it to the next level you can wrap a warm towel around your head. Place cucumbers slices on your eyes and take a nap. That's an order.
Deep conditioned hair may weigh a little bit more than usual, so don't be surprised if your hair feels heavy or very soft afterwards. It's a good sign. My hair usually needs a rest day when I deep condition it, and it's back to normal the following day.
My favorite deep conditioner is the Amika Nourishing Mask. I received a sample of it in a Birchbox awhile ago and fell in love with it. I just ordered the tub using some Birchbox points! It may be the best smelling hair product on the market.
If you don't know where to start when picking out a deep conditioner, ask your stylist. He or she can help you based on what they see your hair may need. Proteins for building, oils for softening, etc.
Happy hair conditioning!