I used to work in SE Alaska with 150 inches of rain a year.
Helly Hansens are the favorite. Or Filson tin cloth.
Check the Alaska Outdoors Forum for a discussion.
If you are in the field in SE, you are going to get wet. When the rain stops the brush is wet. There are plenty of streams to cross. You can wear waterproof gear and get wet from the inside, or breathable gear and get wet from the outside.
YOu can spend a lot of money and get fancy gear, but you are still going to get wet.
In SE, spring and early summer are less wet. Late summer and fall are really wet. The month of Oct in Ketchikan averages 30 inches. The mountains are even wetter.