As most professionals are aware, camera equipment and humid environments do not mix. When moisture gets inside your lens, either because of direct moisture exposure or simply because of very high humidity in our local climate, fungus can begin to grow. Fungus is caused by a combination of this moisture and dust (containing fungus spores) inside the lens. And when this goes unchecked for a while, the fungus will grow and ultimately destroy the coatings on the lens elements, negatively impacting your images and rendering your lens useless (and worthless).
You can get your lens professionally cleaned (or the affected elements replaced), but this is costly and time consuming.
But there is a better solution: silica gel and desiccant packets.
Silica gel is great at absorbing moisture, hence why electronics manufacturers use them when shipping their goods in boxes. You can even find them in lens boxes now.
Place your lenses and memory card in a bag with a 50 gram silica gel packet to protect your gear from humidity.