Does humidity affect the epoxy curing process?

It depends on the type of epoxy being used.

For UltraClear Bar & Table Top Epoxy:

• Humidity is rarely an issue. We recommend keeping it below 60% to avoid potential clouding in the finish. The epoxy will cure properly if the temperature is kept at or above 75°F. Warmer is better.
• Some thermostats are not accurate, so it's always better to set the temperature a few degrees higher than 75°F to ensure that it cures correctly.

For UltraClear Deep Pour Epoxy:

You will want the humidity to be 50% or lower when using Deep Pour Epoxy to have a clear, transparent finish.