Hot and sticky doesn't have to mean slow and gasping. Here's what humid air actually does to your breathing — and how to run through it without falling apart.
What Happens to Your Breathing in Humid Air
Humidity refers to the amount of water vapour in the air. When humidity is high, the air you breathe contains more moisture, which increases the density of each breath. Your respiratory system has to work slightly harder to move the same volume of air, and the sensation of breathing feels heavier and more laboured even at a comfortable pace.
This effect is more pronounced through the mouth. Nasal breathing filters, warms, and humidifies incoming air before it reaches the lungs, which makes the humidity of the environment less of a shock to the system. Mouth breathing bypasses that conditioning process entirely, meaning humid outside air hits the airways more directly.
For Australian runners in summer — especially in coastal cities like Sydney, Brisbane, or Darwin — humidity is a consistent performance factor from November through to March. Understanding how your breathing responds to it gives you a practical edge over runners who just push harder and suffer more.
Nasal Breathing as a Humidity Buffer
The nasal passages condition incoming air before it reaches the lungs. They add moisture when the air is dry, and when the air is already humid, the nasal mucosa still filters out particles and regulates temperature. This conditioning process reduces airway irritation and keeps breathing more controlled throughout a run.
Nasal breathing also promotes the production of nitric oxide in the nasal cavities. Nitric oxide dilates blood vessels and improves oxygen uptake in the lungs — a benefit that's available every time you breathe through your nose and unavailable when you mouth breathe. On a humid run where oxygen efficiency is already under pressure, this difference is meaningful.
Switching to nasal breathing in humid conditions takes practice. Start by maintaining nasal breathing during your warm-up and the first few kilometres. As pace increases, the demand for airflow increases, but runners who have trained their nasal breathing can sustain it at higher intensities than those who haven't.
How Nasal Strips Help in Humid Conditions
A nose strip works by gently lifting the sides of the nasal passages to widen the airway opening. In humid weather, when swelling of the nasal mucosa can restrict airflow slightly, that extra dilation makes a real difference. On The Nose Co's nose strips for running are designed to stay in place in high-sweat, high-humidity conditions — the same conditions where adhesion typically fails on standard strips.
The result is a wider nasal airway that reduces the resistance your respiratory muscles work against on every single breath. Over the course of a long run in summer heat, that reduced resistance adds up. Your breathing muscles fatigue more slowly, your pacing stays more consistent, and you finish feeling less depleted.
Pacing and Perceived Effort in the Heat
Humidity directly affects perceived effort. At the same pace as a cool-day run, humid conditions will make the session feel significantly harder. The standard advice is to run by effort rather than pace in summer — and that's correct — but managing your breathing is what keeps effort in check.
When breathing becomes laboured in the heat, runners instinctively push harder to compensate, which accelerates fatigue. The better approach is to slow the pace slightly, maintain nasal breathing, and let the strip do its job by keeping the airway as open as possible. Running at a sustainable effort in summer builds the same aerobic fitness as faster sessions in cooler conditions.
Practical Tips for Summer Running in Humid Weather
Run earlier in the morning. Humidity is usually lower before 8am, and ground temperature hasn't built up yet. Even a 1–2 hour shift in start time can substantially change how the run feels.
Hydrate before you run. Dehydration thickens mucus in the nasal passages, which increases airflow resistance. Starting a humid run already hydrated keeps the nasal lining in better condition.
Pre-cool where possible. Splashing cold water on your face and neck before the run lowers skin temperature and delays the point at which sweat production ramps up — which is also the point at which nasal strip adhesion comes under pressure.
Don't compare times. Humidity adds perceived effort. A summer run that feels like a tempo session might be a moderate aerobic effort under cool conditions. Chasing times in humid weather usually ends in overexertion.