Humidity is a misleading number when dealing with haircare. Chances are, you know this intuitively already. You know from experience that 100% humidity in the summer and 100% humidity in the winter are not the same feeling. This is because those numbers represent relative humidity. Also, 100% humidity in Arizona is very different from 100% humidity in Florida, even if we're talking about the same time of year.
Dew point is very easy to find out. Just check weather.com, accuweather, or any weather service for your dew point. It'll be posted as a temperature, like 70 degrees.
Dew point is the temperature at which water will condense to form dew or fog. 20 degrees and 100% humidity means the dew point should be at 20 degrees (because the air is saturated). So dew point and humidity are related, but dew point helps you gauge how much moisture is really in the air more accurately, which can tell you a lot about what kinds of products to use.
Dew points are why a lot of curlies find that one product may be a holy grail in the summer, but results in flat, stringy curls in the winter.
What does all this mean for your hair?
Low Dew Points: Negative infinity through 30 degrees
- This is the winter in my hemisphere. It is dry! If there is no moisture in the air, your hair cannot retain any. Your hair wants to be in equilibrium with its environment. This means that if there is no moisture in the air, and your hair has some, it will give up its moisture to the air. If the air around you has 0 figurative drops of water and your hair has 10 figurative drops of water, your hair will expel moisture until the air around it has 5 drops and it has 5 drops. This is the battle of winter. You have to continually replenish moisture because your hair will be continually giving it up to the dry air in low dew points.
- Deep treatments, rich conditioners, hair butters, creamy leave ins, and humectant-free products will help you in winter.
- Humectants are products which work to make that equilibrium between your hair and the environment happen faster and more efficiently. As we'll see, they are your friend in moderate dews, but your mortal enemy in low dews, because they will just be pushing moisture out of your hair and into the air! Common humectants are glycerin, panthenol, honey, propylene glycol, and vitamin B5.
Moderate Dew Points: 40-60 = moist and happy!
- This is a favorite time for many curlies.
- The air is now comfortably moist, so the air now has the 10 figurative drops, and your hair has 0 (well hopefully you've been taking better care of it than that so it isn't that dry, but this is for illustrative purposes). You want to use products that will help pull some of that moisture from the air into your hair.
- Humectants will pull moisture into your hair to balance it out. Don't ignore your moisture treatments, but you can now use lighter products.
High Dew Points: 60 and up = muggy and 80s hair revival.
- Some curlies will outright skip rinse out conditioners.
- Humectants become somewhat dangerous here, because they can pull too much water into your hair, making it swell and poof.
- Here, you will want to use antihumectants. These ingredients are water repellents. Castor oil, beeswax, coconut oil, palm oil, olive oil, and shea butter are antihumectants.
- A hard hold gel will be your friend in these muggy conditions as well, as these gels create a barrier around hair strands, which will block some of the moisture from the air.