As an Amazon Associate I earn from qualifying purchases. Product links below are affiliate links.
A breathable waterproof jacket lets moisture move out through its fabric, but it cannot guarantee that you never feel sweaty. Your activity, layers, weather and the garment’s ventilation all affect how comfortable it feels.
Table of Contents
Know which rating you are reading
Rab’s breathability guide explains two common measurements. MVTR describes moisture transfer through an area of fabric over time; higher values indicate more transfer under the same test. RET measures resistance to evaporation; lower values indicate better breathability under comparable testing.
| Measurement | Direction to look for | Comparison caution |
|---|---|---|
| MVTR | Higher under the same test | Check method and units |
| RET | Lower under the same test | Do not compare the number directly with MVTR |
Different laboratory methods can produce figures that are not directly comparable. If a seller gives a breathability number without units or method, ask for the underlying specification before ranking it against another jacket.
Separate fabric transfer from ventilation
A membrane’s performance and an opened vent are different ways of managing moisture and heat. Underarm vents or a controlled front opening can help during hard work when the weather permits, but they also create openings that must be managed in rain.
The Rab Downpour QWI-06 combines a stated MVTR specification with underarm vents. Compare the Downpour jacket on Amazon UK as an example of looking at both fabric and garment features.
Adjust before you become soaked
Think about how warm you feel when you start walking uphill or carrying equipment across the site. Remove an unnecessary insulating layer or adjust ventilation before heavy sweating, provided the conditions allow it.
Choose layers that fit without bunching and avoid packing the shell so tightly over insulation that movement becomes restricted. The same jacket can feel different over a light base layer and a thick fleece.
Consider rain and surface condition
A face fabric that becomes saturated can feel heavier and clammy. That sensation is not enough on its own to prove water has penetrated the waterproof barrier. Inspect the garment and follow its care guidance when performance changes.
Keep pockets and vents configured for the weather, and check whether pack straps obstruct the areas you expect to ventilate. A useful feature is one you can actually operate while wearing the rest of your kit.
Choose for the activity
For energetic walking, ventilation and moisture management deserve attention alongside weather protection. For sitting at camp, warmth and coverage may become more important. Use comparable ratings as evidence, then try the complete layering system rather than expecting one laboratory number to predict personal comfort.
Our hydrostatic-head guide explains the separate water-pressure rating. If comfort has changed since the jacket was new, also work through our wetting-out and care guide.
Continue with our waterproof jacket comparison.
Reviewed 10 September 2026. This guide is based on published specifications and guidance.