Be honest: at some point, most of us checked the dew point before deciding which gel to use. We screenshotted the charts, memorized our “safe” range, and treated the weather app like a styling oracle. I did it too. If the dew point crept past some magic number, I mourned my wash day before it even started, and when a routine flopped, the forecast got blamed long before I ever looked at my own technique.
It made us feel like we had finally cracked the code. The catch is that the code was mostly made up. Working with my friend, a hair scientist and cosmetic formulator with a PhD in chemistry, I learned that the dew-point rulebook we all passed around is far shakier than it sounds, even though the thing underneath it, weather changing your curls, is very real.
Short answer: dew point is just a way of measuring how much moisture is actually in the air. It is real and it matters, but the specific dew-point rules curlies follow are a community heuristic, not validated science. Your curls change with the weather because hair itself takes up water and swells, so the fix is hold and healthy hair, not chasing dew-point numbers.
Does Dew Point Really Control Your Curls?
Not the way the dew-point charts suggest.
Dew point is the temperature at which air becomes saturated, which makes it a good measure of how much actual moisture the air holds; the higher it is, the more humid it feels. Paying attention to whether the air is humid or dry is genuinely useful.
What does not hold up is the popular system of assigning curl behavior to exact dew-point ranges and switching humectants in and out by the number; that is a community heuristic, not validated science.
Your curls change because hair is hygroscopic: in moist air it takes up water, swells, and the hydrogen bonds that hold curl shape reset, which causes frizz and loss of definition. [1]
How much that happens depends far more on the condition of your hair and the hold of your styler than on a temperature reading. So the goal is not to track dew point to the degree; it is to build a style with enough hold and keep your hair healthy.
Humidity vs Dew Point: What’s the Difference?
They get used interchangeably, but they measure different things. Relative humidity is a percentage: how much moisture the air holds compared with the most it could hold at that temperature.
Dew point is a temperature: the point at which the air would be saturated, which tracks the actual amount of moisture present. Because warm air can hold more water than cool air, two days with the same relative humidity can carry very different amounts of moisture, which is why dew point gives a steadier sense of how humid it really is.
For curly hair, the practical takeaway is simple: a higher dew point means more moisture in the air for your hair to take up. That is the whole of what it tells you; it does not prescribe a product.
Why Your Curls Change With the Weather
Hair is hygroscopic, so the water it holds rises and falls with the moisture in the air around it. [2] On a humid, high-dew-point day, the strand takes up extra water and swells, and the hydrogen bonds that hold your curl shape break and reform in new positions; that is what makes clumps separate and frizz build through the day. [1,3]
In dry, low-dew-point air the opposite happens, and curls can feel stiffer or rougher. The condition of your hair matters too: more damaged, more porous hair takes up and loses water faster, so it frizzes and reverts more.
None of this depends on a particular humectant being present; it is the hair itself responding to the weather.
For how individual ingredients fit in, including what humectants and so-called anti-humectants actually do, see my companion guide, Humectants vs Anti-Humectants: Which Does Your Curly Hair Actually Need?
The Dew Point Rule: Does It Actually Work?
You have probably seen the charts: curl behavior sorted into tidy dew-point ranges, dry and stiff below about 35 degrees, a magical sweet spot in the 40s, and frizz and chaos above 60.
They circulate everywhere in the curly community, and full confession, I kept one on this very blog for years. (Yes, I am shaking my head at myself too.) But when you know better, you do better, so here is the honest version: those numbers are a loose generalization, not a validated rule.
Dew point is only a proxy for how humid it is, and how your hair actually responds depends on its condition and the hold of your styler far more than on a temperature. You do not need a dew-point app or a chart taped to your mirror.
Noticing whether the day is very humid, comfortable, or very dry is plenty; the rest is about how you style and how healthy your hair is.
Why the Whole Formula Matters More Than One Ingredient
It is tempting to blame a single ingredient when your curls suddenly misbehave, but a product is a whole system, not one hero ingredient. The concentration of each ingredient, the conditioning agents, the hold system, the amount of film-forming polymer, and even the thickness of the formula all shape how your hair responds.
Two gels can both list glycerin near the top and still behave completely differently, because one is backed by a strong film-forming hold and the other is not. This is exactly why an ingredient list cannot reliably predict how a product will perform, and why chasing or avoiding one ingredient rarely solves a weather problem on its own.
The same goes for the oils, butters, and silicones sometimes called anti-humectants: what matters is how they are balanced within the finished product, not the word on the label.
The most reliable approach is to judge a complete product by how your hair responds to it over a few wash days, rather than ruling it in or out by a single name on the back of the bottle.
How to Spot Humectants on a Label
If you still want to read labels, here is the honest version. Humectants are easy to recognize once you know the names: glycerin, propanediol, propylene glycol, sorbitol, sodium PCA, panthenol, aloe, and honey.
Ingredients are listed roughly in order of how much is in the product, at least until you reach the ones under about one percent, which can appear in any order, so a humectant near the top is present in a larger amount than one near the end.
What that does not tell you is how the product will behave on your hair, because the hold system and the rest of the formula matter just as much.
Use the label to understand what a product is built around, then let your own results decide. My humectants versus anti-humectants guide has a fuller label breakdown.
How to Adjust Your Routine by Weather
Humid, high-dew-point days
This is when hold matters most. Build a style that can resist the hair’s urge to swell:
- Apply your styler to soaking-wet hair so curls clump evenly.
- Use enough strong-hold gel to form a firm cast over the whole head.
- Dry fully by diffusing or air drying before you go out; damp hair invites frizz.
- Scrunch out the cast only once the hair is completely dry.
- Keep your hands off during the day; touching breaks the film and lets frizz in.
Dry, low-dew-point days (and winter)
Dry air pulls water out of the hair, so curls can feel stiff or rough. Lean toward conditioning for slip: a richer leave-in, a little oil for surface smoothness, gentler cleansing, and protecting your hair from drying indoor heat. This is about conditioning the surface so the hair behaves better, not adding water to the strand.
In-between days
Most days are not extreme. Keep your routine simple and nudge your hold up or down a little rather than overhauling everything for one humid afternoon.
Do’s and Don’ts for Humid-Weather Curls
Often it is styling habits, not the weather itself, that make curls harder to manage. A quick guide:
| Do | Don’t |
| Apply stylers to soaking-wet hair so curls clump evenly | Pile on too much product or layer too many stylers |
| Use enough hold to form a firm cast | Touch or scrunch the cast before it is bone-dry |
| Dry fully (diffuse or air dry) before going out | Leave the house with damp hair on a humid day |
| Scrunch out the cast only once hair is completely dry | Refresh heavily day after day |
| Keep refreshes light and protect curls at night | Keep adding oil to the surface through the day |
| Nudge your hold up or down with the weather | Overhaul your whole routine after one humid afternoon |
If Your Style Isn’t Holding Up, Here’s What’s Usually Behind It
Curls that frizz, puff, or fall flat in humidity get blamed on humectants all the time, but that look is not a humectant fingerprint; the same symptoms come from a handful of far more common causes. Before you swear off an ingredient, check these first:
- Frizz and puffiness by midday: usually too little hold to resist the hair swelling. Try a firmer-hold gel and make sure you build a full cast.
- Curls that go soft, floppy, or lose definition: often too much product or buildup weighing them down. Use less, and cleanse buildup with a regular shampoo.
- Curls that separate or frizz before the style sets: frequently hair drying too slowly in damp air. Dry fully by diffusing or air drying before you go out.
- Frizz that creeps in through the day: commonly from touching, refreshing, or adding oil on top too often. Keep your hands off and refreshes light.
- Persistent frizz no matter what: often underlying damage, since more porous hair takes up water and frizzes faster. Focus on protecting the hair and reducing heat and friction.
Notice that none of these point to a single ingredient. The fix is almost always hold, technique, cleansing, or hair health, and the only way to know what works for you is to change one thing at a time and watch how your curls respond.
Products That Hold Up in Humidity
Since hold is the real humidity defense, reach for film-forming stylers with staying power on a smooth, conditioned base. This is a different lineup from the picks in my humectants versus anti-humectants guide, which explains why film-formers work, so you have more options to try:
- Leave-in smoother (foundation): Olaplex No.6 Bond Smoother. A humidity-resistant leave-in cream whose cationic conditioners and silicones smooth the cuticle and tame frizz, laying a sleek base. It is marketed as a bond builder, a claim the wider science still treats as unsettled, so judge it on the smoothing you can feel; it adds smoothness, not hold, so pair it with a styler below.
- Strong-hold gel, premium: Curlsmith In-Shower Style Fixer. Built on Polyquaternium-69, a film-forming polymer chosen for humidity resistance; it forms a firm cast you scrunch out for long-lasting definition.
- Strong-hold gel, budget: Eco Style Gel (Curl & Wave or Olive Oil). A few dollars, PVP-based for a firm everyday cast.
- Strong-hold mousse: Mielle Pomegranate & Honey Curl Defining Mousse with Hold. PVP and polyquaternium-55 give a non-sticky hold with volume; layer it over a gel or use it alone.
For Wavy Hair: Lightweight, Strong Hold
Waves need hold without weight, so lean light and skip heavy creams and butters that flatten a looser pattern.
- Bounce Curl Light Creme Gel: a lighter creme gel built on a VP/VA film-forming polymer; enough hold to fight frizz without weighing waves down.
- A light mousse: the Mielle mousse above, used sparingly, adds hold and volume; mousses are a wavy favorite for exactly that reason.
Whichever you pick, the routine matters more than the brand: a conditioned base, a film-forming styler with real hold, dried fully, then scrunched out. Test one change at a time and keep what holds best for you.
Frequently Asked Questions
What is dew point for curly hair?
Dew point is the temperature at which the air becomes saturated with moisture, which makes it a good measure of how much water is actually in the air. For curly hair it is simply a more reliable read on how humid it really is than the relative-humidity percentage. A higher dew point means more moisture in the air for your hair to take up, which is why curls tend to swell and frizz more on high-dew-point days. That is all it tells you; it does not dictate a product.
What dew point is best for curly hair?
There is no single best number, despite the charts that say so. Many people feel their curls behave most predictably in moderate conditions and struggle more in very high or very low dew points, but that is a loose generalization, not a rule. How your hair responds depends far more on its condition and the hold of your styler than on a specific dew point. Rather than chasing a number, notice whether the day is humid or dry and adjust your hold accordingly.
Do I need to follow the dew point rule?
No. The dew-point rules circulating online, with exact ranges for when to use or avoid humectants, are a community heuristic, not validated science, and they tend to make routines more confusing. You can loosely notice whether the air is very humid, comfortable, or very dry and lean toward more hold or more conditioning, but you do not need an app, a chart, or threshold numbers. Watching how your hair actually behaves is more reliable than any forecast.
Is glycerin bad for curly hair? (The glycerin debate)
This is one of the most argued-about ingredients in the curly community, blamed for frizz in humidity and for drying hair out in winter. The reality is less dramatic. Glycerin is an ordinary humectant found in countless curly products, and your hair’s response to the weather matters far more than the glycerin itself. Some people find very glycerin-heavy products feel puffy in high humidity or less flexible in harsh winter heat, but plenty perform beautifully year-round. You do not need to avoid it; judge the whole product on your own hair rather than ruling out the ingredient.
How do I stop my curls from frizzing in humidity?
Use a styler that forms a firm film and holds the curl, such as a strong-hold gel or a style sealed with a light oil or silicone film, so the hair resists swelling and keeps its shape. Apply to soaking-wet hair, dry fully before going out, and scrunch out the cast only when bone-dry. Keeping your hair healthy helps too, since damaged, porous hair frizzes faster. Test a couple of approaches and keep the one that holds best.
References
- Robbins CR. Chemical and Physical Behavior of Human Hair. 4th ed. New York, NY: Springer; 2002.
- Barba C, Martí M, Manich AM, Carilla J, Parra JL, Coderch L. Water absorption/desorption of human hair and nails. Thermochim Acta. 2010;503–504:33–39.
- Marsh JM, Gray J, Tosti A. Healthy Hair. Cham: Springer International Publishing; 2015.
