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Waterproof Jackets

Why are they compulsory?

Wet clothes can lead to hypothermia in even mild conditions. Add to that heavy rain accompanied by wind and you have a recipe for disaster. Hypothermia is a condition in which your body is losing heat faster than it can generate it. Mental confusion is a consequence of hypothermia and it often leads to very poor survival choices. Hypothermia is an emergency condition that can quickly lead to unconsciousness and death if heat loss continues. You can prevent hypothermia be ensuring that you have a waterproof jacket in your backpack during any trail run where rain is a possibility.

What’s the difference between water resistant and waterproof?

Water resistant means that the material the jacket is made of has been treated with a water repelling coating and will shed water. Many water resistant jackets also have a very thin waterproof membrane, this is breathable and allows sweat out but prevents water from getting in. Even though a jacket has a water repelling coating and has a waterproof outer membrane it’s still not waterproof.

Waterproof jackets usually have a water repelling coating, a waterproof membrane and taped seams. Taped seams are heated treated seams that close up the holes created by stitching. The simplest way to see if a jacket is waterproof or not is to check to see if it has taped seams. The tape will be on the inside of the jacket and run the full length of all the seams. If it’s not taped – it’s not waterproof.

Just how waterproof is it?

Waterproof jackets have a waterproof rating. The higher the rating the more waterproof the jacket is. The rating is given in millimeters and is a measure of the amount of water in a 24 hour period, a fabric can withstand before water gets through.

< 1 500 mm

Water resistant. Good for – Dry conditions or a very light rain.

1 500 mm – 5 000 mm

Waterproof. Good for – Light to average rain.

5 000 mm – 10 000 mm

Very waterproof. Good for – Moderate to heavy rain.

10 000 mm – 20 000 mm

Highly waterproof. Good for – Heavy rain.

A rating of 5 000 – 10 000 is suitable for most trail runs in South Africa.


Like all our running clothing we need the sweat of our bodies moved away from the skin. A rain jacket with poor breathability will quickly gather sweat on the inside of the jacket and it will feel as if the jacket has leaked. This can be a terrible realisation halfway through a race. Jackets are manufactured with a breathable material which allows the perspiration to move from the inside to the outside of the jacket. Side or ‘pit’ zips are installed on some jackets which creates extra ventilation helping to keep the body cooler and allowing some of the moisture laden air inside your jacket to escape.


As trail runners we want a rain jacket to fit as close to the body as possible. Extra material gets blown about by the wind which can push you around in heavier winds. Extra material also creates a lot of noise as wind blows it around often making it impossible to hear anything which might include the noise of a rescue. Consider whether you’re going to have your pack inside or outside your rain jacket and what additional clothing you might want to wear under the jacket.

Although you want a close fit it shouldn’t in any way impact on a full range of movement, least of all your running gait.

Additionally look for the following :
  1. Long enough to cover you when your arms are raised over your head
  2. Extra length in the back to cover the gap between shirt and pants
  3. Elasticized bottom to stop the jacket from riding up as you move
  4. Thumb loops to keep the sleeves from riding up your arms as you move
  5. Adjustable hood that can be snugged down around your face without blocking your view
  6. A hood with a peak to keep rain off your face


You are going to have to carry this jacket with you whether it rains or not. Look for a jacket that is very lightweight and packs down to as small a size as possible. Many of the jackets designed for trail running and fast packing will fold into a pocket or a pouch.

Hopefully I’ve explained why you need it and what you should be looking for. TIP – put your rain jacket on before its starts to rain!

Happy Trails!