What does the camping tent waterproof index mean?

Update:06-05-2020
Summary:

Tents with a waterproof index of copy800MM-1200MM can p […]

Tents with a waterproof index of copy800MM-1200MM can prevent small to medium rain. Tents with a waterproof index of 1500MM-3000MM can be protected from moderate to heavy rain. Tents with a waterproof index of more than 3000MM are generally treated with high-temperature / cold-resistant technologies, and can be used in various environments.
According to the type of tent, the waterproof index of leisure tents used in the park should be within 1000MM; the waterproof index of family camping tents should be above 2000MM, and the waterproof index of mountain tents should be above 5000MM.
waterproof tents