Friday: This may be the worst weather day of the event, which is always a good thing that you'll get it out of the way first. Even though it may not be ideal, it won't be bad either, with temperatures in the 40s for the start and moving through the low to mid 60s by the afternoon. The reason this will be the worst day will be because of the winds, which will be gusty behind a cold front that passes through in the morning. Winds will be out of the northwest around 10 to 20 mph, so be prepared to be walking into a stiff breeze at times.
What to Wear: I would dress in layers as you'll need it in the morning then will need to shed it in the afternoon. A long sleeve shirt and tights should be good with a t-shirt for the afternoon. With the wind, it will also feel colder than it really is so be sure to take that into account. A couple things you may want to wear are a hat, sunglasses, and even suntan lotion as you'll be outside for a while. Also, as I'm a huge runner, you may want to wear some body glide as you don't want to chafe on your first day out!
Saturday: The start of the weekend will be the coldest part of the walk, with lows around 40 degrees. The remainder of the day looks great with high temperatures in the lower 60s under mostly sunny skies. Winds are also expected to be light.
What to Wear: Be sure to dress in layers again as this will be another chilly day to start but you could easily get away with a t-shirt by the afternoon hours. Don't forget your hat and sunglasses with full sunshine as well as some suntan lotion.
Sunday: Ah you've almost finished!! Sunday is looking great with mostly sunny to partly cloudy skies and warmer temperatures. Lows won't be nearly as cold as they settle into the upper 40s to near 50 degrees. High temperatures will push into the lower 70s, making for a fantastic afternoon for everyone to celebrate their accomplishments.
What to Wear: Layers will still probably be the way to go as starting temperatures around 50 degrees will be chilly but it should warm up much quicker so be sure to have a t-shirt handy. Once again a hat and sunglasses along with suntan lotion will be good to have.