Humidity and Temperature Tolerance is how well a bee can adjust to a climate that is not their favorite. This is a number scale ranging from -5 to +5 for both stats, and can work both ways for some bees.
If a bee has Normal/ Normal for their temperature and humidity, and up 1 for temperature tolerance and Down 1 for humidity tolerance, then the bee can work in Normal and Warm temperate climates and Normal and arid humidity climates.
A bee that has Both 1 in temperature tolerance and up 1 in humidity tolerance can work in Cold, Normal, and Warm temperate climates, and Damp climates.
While there are six temperature climates, there are only three humidity climates. Having more than Both 2 in humidity tolerance (ex: using the acclimizer) is wasteful.
Icy > Cold > Normal > Warm > Hot/ Hellish
Hellish acts as Hot for the purposes of temperature. This is simply an indication that the bee requires the Nether biome.
Humid > Normal > Damp