In my part of Missouri, the average daytime humidity during the first 20 days of July was 95%. Not only does this make a bee veil pretty uncomfortable, but it also makes it hard for our bees to dry their honey to the same degree as a colony in Arizona, where the average humidity this month has been closer to 40%. This is because honey is hygroscopic, which means it readily absorbs moisture from the air. Colonies deal with this by extracting water while they're transfering nectar from bee-to-bee, fanning the nectar once it's in open cells, and then capping those cells with wax once the honey is sufficiently dehumidified. The resulting low moisture content and protective wax are a couple factors that give honey its superpower of being able to last indefinitely without spoiling.
Honey is particularly vulnerable to absorbing moisture while it's being processed (hygroscopic rehydration). At this point we've taken it from the bees, who have been working so diligently to remove water. We're also cutting away the protective wax cappings. During this phase I'm checking my moisture levels often using a honey refractometer. When I uncap a frame and it measures at 18-19% moisture, I don't have much wiggle room so I need to ensure that number doesn't climb while they honey is exposed to the air. Most of us don't have a dedicated honey house, so one option is to use a "dry room" to control the environment for your supers and honey buckets. A dehumidifier in one of these little tents can easily create Arizona-like weather and negate the moisture uptake you get during extraction and bottling; potentially being the difference between honey that lasts 2000 years and honey that ferments next spring.
My bees will never produce honey that rivals the moisture levels enjoyed by beekeepers in dryer areas. This is perfectly fine because I love our honey, and wouldn't want to change it. Frankly, when I hear of a local beekeeper selling honey at 15% moisture content, I'm curious (suspicious) about how they managed such a low number in such a humid environment. But if you're like me and want to offer raw honey with minimal manipulation, check your moisture levels to ensure they're below 18.5% and keep your processing area dry to minimize water uptake.