Not all natural dangers are handled by effect cards. Severe environmental conditions such as blizzards and heat waves can also threaten a character.
Whilst a character will have mundane equipment suitable for the environment this does not extend to extreme conditions. A party of adventurers exploring in the mountains will have appropriate cold weather gear but this does not guarantee them safety. If caught in a severe blizzard they will still have a real chance of dying from the cold.
The Game Leader should assign a dice value to the environment's attack, e.g 1d6+3 high winds with 1d6+6 cold, and a length of time each attack will take. This could be seconds for characters caught in a tornado or 24 hours for anyone trapped in blizzard. For each attack the environment makes, the characters have a resistance action using whatever cards they can justify plus situation bonuses.