High quality outdoor clothing is worth every penny if it keeps you warm and dry.  We will sail and explore in many extremes, and the proper dress can be the difference between an exhilarating experience or misery and exhaustion.
With the clothing and foul weather gear available to us today, it is possible to be completely comfortable while standing a 3 or 4 hour watch in the pouring rain.  As a matter of fact, it is a real blast when you feel properly protected from the elements, and yet you are smack in the middle of a gale.  You will have less fatigue and more confidence.   
For our trips in cooler Spring and Fall seasons, you needn't run out and buy a bunch of new gear as long as you have an outer shell that can cut the wind, and can use multiple layers of underclothing.  Wicking under garments, such as Under Armor are very helpful.  It makes a big difference to be able to tighten wrist, and ankles cuffs and keep your neck and head covered.
Make no mistake, Gill, Helly Hanson and even West Marine have some great foul weather gear that is ideally suited to wet sailing conditions.  But I've also seen some pretty slick camouflage hunting wear from Cabelas that did a fine job in the nasty weather. 
Denim jeans aren't well suited to sailing as they can restrict movement, and once soaked with salt water, I can almost guarantee they will be damp and heavy the remainder of the trip.  Loose fitting light-weight cotton pants other than denim work well, and there are other outdoor fabrics designed to wick moisture from the skin and dry very quickly.
For our Summer trips, shorts and t-shirts may be the rule, but evenings can be chilly, and the wind can get very cool offshore.  I recommend a sweater or sweatshirt and a quality windbreaker or light foul weather jacket.  If we are on a Cruising Passage, plan on some form of water proof foul weather pants as well.
Please limit your clothing luggage to one soft sided duffel.  I own a nice soft sided bag with handle and wheels and it works nicely as my air travel carry on bag.  This may seem like a challenge, but please make a game out of minimizing the clothing and stuff you bring along.
Digital cameras - These are a must of course!  But please take care as I have seen several go snap, krackle and pop when they got wet.  If you are not using the camera, I recommend you store it in a safe dry place.  The viewing screens also get easily cracked.  The survival rate is not good when left out, even in the salon or nav station. 
On the Plein Air expeditions, we will often be going ashore in the dinghy, and it is hard to jump ashore without immersing your feet, so a pair of pull on rubber boots are very comfy indeed.  Or, you may opt for sandals and rolled up pant legs.

Gear for Plein Air Expeditions

... suggestions not requirements

Gear for Cruising Passages

... suggestions not requirements

One Soft Sided Bag
Foul Weather Top and Pants
Deck Shoes or Booties
Layered Clothing
Sweater
Hat
Sunglasses
Gloves
Inflatable Life Vest
Harness and Tether
Small Flashlight
Rigging Knife
Light Sleeping Bag
Seasickness Meds

Warm and Dry!

Hat and Sunscreen!

One Soft Sided Bag
Light Foul Weather Top and Pants
Deck Shoes
Mid-calf Rubber Pull On Boots or Booties
Hat
Sunglasses
Inflatable Life Vest
Light Sleeping Bag
Art Supplies for 2 to 3 Days
Canvas Boxes - No more than 2 please.
Easel
Seasickness Meds

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