Question: What if my area experiences prolonged cloudiness, wet conditions?
Answer: If you get a good bit of cloudy, rainy weather in late spring or fall, expect fungal diseases to show up. Watch closely, then treat with an appropriate fungicide at first signs of an outbreak. Expect, too, for your healthy, vigorous plants to wilt temporarily when they're exposed to full sun for the first time in several days.
If you continue to have troubles with plants in one particular part of your garden because of excessively wet soils, consider installing guttering and downspouts, also in-ground grates and drains, and perhaps even a French drain to carry the excess water away to a storm sewer or to the curb.