Tents are made from either canvas or polyester, two fabrics that are not water resistant on their own. To prevent leaks, manufacturers coat these fabrics with either Teflon or polyurethane, as these materials add water resistance while still maintaining the breathability of the fabric.
Once coated, the water resistance of tents is measured through a hydrostatic head test with results expressed in millimeters.
According to the legal requirements, a tent must have a hydrostatic head (HH) of at least 1,000 to be considered waterproof. However, 1,000 mm fabrics might not withstand more than light rain.
For this reason, you should look for a HH rating of 3,000 or over if you want to camp in all seasons and stay dry even in a downpour.
The table below should help you understand the HH rating of the most popular tents on the market:
Hydrostatic Head (mm)
Light rain, dry snow
Moderate rain, average snow
Heavy rain, storms, wet snow