You should expect & plan for heavy rain every day. A few tips:
- a synthetic-filled sleeping bag is preferable to down-filled for this hike (just in case you get it wet)
- cotton is poor, wool better, synthetics best and lightest.
- cotton is quick to get sweat soaked and slow to dry. Bring clothing made of quick-drying, wicking synthetic fabric.
- most hikers bring socks of wool, thick acrylic, or wool-acrylic blends. Most wear them over a thin wicking sock liner. Be aware that your socks will probably be the last clothing to dry. There's a good chance your boots will still be wet in the morning.
- a down vest is great & makes a soft pillow
Many thin layers are lighter & warmer than 1 thick garment
If you get chilled, climb into your sleeping bag. Cuddle-up. Do anything you can to warm-up if there's a chance of hypothermia.
Light fleece garments are warm, even when wet, & they dry quickly.
Keeping Dry
Since you will have rain, consider bringing tarp(s) & plenty of tie-up ropes. Protect yourself from the elements while cooking dinner. Tarp-tying is a much underrated art & science, particularly in high wind.
Most campsites do not have cook shelters. Be prepared to cook in the tent vestibule (a safety risk) if you do not have a tarp.
Many campsites have restaurants where you can buy dinner rather than cook — if the weather is bad.
Bring a backpack cover. You'll be glad you did. Check that it fits your pack when fully loaded. Many XL (extra large) covers are too small for extra large backpacks.
Waterproof EVERYTHING inside your pack. Stuff sacs should be waterproof. Plastic bags are OK but they rip. Waterproof stuffsacs are only slightly heavier and far more reliable.
Consider stuffsacs normally used for kayaking. These are heavier than other waterproof stuffsacs, but not much.
Bring extra plastic bags & ziplocs.
Double-bag vulnerable valuables such as cameras.
