Three d20s with the rules-appropriate markings to determine Wind, Precipitation, and Temperature each day. Two d12s marked in increments of 10°, 20°, 30° and 40°F, these dice roll for the temperature deviation on hotter- and colder-than-normal days.
Rolling weather allows players to have fun with those lesser-used aspects of their characters. They can get creative about how they’re using the weather to their advantage, or adjusting their plans to the new, random challenge.
For the DM, weather is a beautifully simple keystone to an adventuring day. It bolsters immersion with a few sentences. It punctuates the adventuring day, giving you something to transition with during an otherwise uneventful watch “you feel the air get cooler as clouds roll in.” A particularly bad day of weather can add an additional layer of strategy to encounters, or an opportunity for a character to shine in a new way.
Weather plays a crucial role in storytelling and narratives. Perhaps the enemies tracks became impossible to follow as snowfall began to cover the ground... but when the squall passed, a distant camp was revealed by the rising smoke of fires kept roaring for warmth in the cold.