Rain Jacket? Yes. Rain pants?

[John Nelson]

I take rain pants. They are light, and they are good for lots of things. I only wear them riding if it is cold, but they keep me dry in camp when it's raining, which is even more important than keeping me dry while riding. And rain pants are great protection against mosquitoes. I also wear my rain pants when I am washing everything else I own.

[staehpj1]

I have found that the  standard leggings which are tight and not baggy, repel water and keep me warm down to the low 50's, so no rain pants if the tour is unlikely to get that low.

To that point it may depend on your route or the timing of your start and finish.

OTOH, any coast to coast trip will have some high altitude riding where it might be cold.  Some wind pants may come in handy there.  I have some rip stop nylon ones that weigh 2.5 ounces (they were actually sold as dance warmup pants).  They aren't really waterproof, but I treated them with DWR spray.  You could consider having something for only part of the trip mailing to and from home or maybe picking up something if you find you are or will be encountering worse weather than you expected.  I have carried or not carried depending on the trip, most often taking wind pants and wind shirt, but sometimes taking actual lightweight rain gear.

Frogg Toggs makes a variety of rain wear some of their stuff is fairly light weight (12.8 oz for two piece suit) and cheap (under $20 for a suit).  You could pick up or have a suit sent to you if you decide you need it or carry one from the start.  Coated nylon suits can also be light and cheap.  Also some folks use ponchos.  I have never ridden with one, but some claim they work okay.  They are great in camp.  Frogg Toogs makes inexpensive ones.

[GrnMtns]

I'd love to find some water repellent leggings that are stretchier than rain pants, and don't rely on a spray finish that wears off after a few days on the road.

[staehpj1]

I'd love to find some water repellent leggings that are stretchier than rain pants, and don't rely on a spray finish that wears off after a few days on the road.

A few days?  I sprayed mine until heavily soaked with DWR spray and have used them for years without retreatment.  I think it was Nikwax brand, but am not sure.

[El_Chupacabra]

I've used rain jackets and pants riding, and have the same issues with sweat inside the rain gear.   It is nice to have them once stopped though.

I have a bike specific rain poncho that I like more than the jacket/pants combo for riding.  Mine is from Vaude, has loops to stay on your hands (out on the handlebar). Poncho + full fenders seems to work pretty well. Not great in wind though - it's kind of a sail.

[canalligators]

When it rains, I expect to get wet, from the outside or the inside.  What you really need when riding in the rain, is to be able to SEE, and to be WARM and VISIBLE.  If it's raining really hard, I take shelter and wait it out.

[Ty0604]

I carry rain pants, jacket, booties and helmet cover. The pants are Columbia, the jacket Showers Pass, the booties Pearl iZUMi and the helmet cover some off brand.

I only put them on during downpours though. Like when I was riding in Hurricane Sally this past September between Gulf Shores and Pensacola. Otherwise it's too much of a inconvenience. I do like the peace of mind knowing I have them though.

[canalligators]

Ah, right... I definitely use some sort of helmet cover.  It really annoys me when rain runs down my head.

[misterflask]

Usually:
A Marmot precip rain jacket - nice and light but single layer and icky on bare skin.
Rivendell rain pants (no longer made) - multi layer and not overly heavy. 
Vaude cycling gaiters - Love these for keeping shoes dry even without rain pants
J&G helmet cover - Doesn't weigh much but sort of belt and suspenders when wearing a jacket hood under your helmet
Waterproof mitten covers - For cold weather.  No use having gloves if you can't keep them dry.  Only weigh 4oz.

Some variations:
My J&G waterproof breathable jacket is my favorite rain jacket on and off the bike.  A little heavier than the precip but really comfy and warm with its multi-layer construction.  I think it's a great value if $300 Gore-tex makes you flinch.  Optional hood is kind of meh, but ok under a helmet.
Precip rain pants - single layer and fairly light.  Serviceable but a little billowy
J&G shoe covers - these needed additional waterproofing and tended to allow my pants to climb above them.
In warm weather I use a skirt made from a drawstring garbage bag instead of rain pants.

I have a pair of Showers Pass touring shoe covers but wouldn't tour with them as they are heavy and you can't clip through them.  They are super-waterproof though.  I use them to ford streams on gravel rides while keeping my shoes dry.

Don't forget a saddle cover if you ride leather.  I have mostly Brooks, but the Aardvark seems ok too.

Straying from rain gear here, but the J&G touring shorts are really nice.  You can look like a normal human on a ride while having a touch of padding. They dry pretty quickly and make passable swim trunks.

[hikerjer]

J & G ?

[misterflask]

J&G can be found at bicycleclothing.com

They apparently need some Search Engine Optimization.

[Westinghouse]

Frog Togs at Wal Mart, $20.00, feather weight, breathable, waterproof. Gorilla tape the seams in the crotch if you cycle in them.

[misterflask]

<<Frog Togs at Wal Mart, $20.00>>

Wow, thanks Westinghouse.  I own a lot of hiking and cycling raingear, but these are going to find their way to near the top of the stack.  Just bought a set on your recommendation and rode them for a rainy commute.  They're respectable by any standard and awesome for the price.

Weight at less than a pound for the set is hard to beat.
Inside surface is less sticky than my fancy Marmot precip jacket.
No niceties like pit zips or leg zips for ventilation, though.
Unexpectedly nice zippers and snaps.
They need leg bands to stay out of the chain, but
I was able to pull these on over my size 14 clown shoes.
I have -really- long legs but M/L were plenty long.

tnx agn
bcs

[jkbrooks]

I use a Marmot PreCip rain jacket since it's farily lightweingt and some old single layer lightweight rain paints which I annually coat with a waterproof spray. Seems to work pretty well for me but it's hardly perfect. But as others have a testified, in hiking and cycling, if you're going to put forth any exertion, you're going to sweat, some more than others, and get wet from the inside. I use a cheap shower plastic shower cap from Walmart to cover my helmet but have yet to come up with a satifactory method of keeping my feet dry. I generally go with wool socks inside my shoes. I still find the best defense is to make sure you have dry clothing to change into when you stop. Otherwise, you're going to be screwed.

I've just started using these neoprene socks. They keep my feet plenty warm. I wear wool socks underneath. They're not really waterproof though. I figure I can put up with the wet. Allows me to wear my cycling shoes instead of cycling boots in the rain. The boots keep my feet dryer but also restrict my range of motion just a tad. I've not done a multi day tour though. Just day rides. I also got some Showers Pass similar type socks. The Shower's Pass ones seem a bit more sturdy but they're a bigger pain to get on & off. My feet sweat in them. I suspect "breathable" is a relative term.
https://www.amazon.com/gp/product/B000O5WQXA/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

[EmilyG]

Once I get chilled, it is difficult to get warmed up again, especially my legs. So I take and wear rain pants. I found these Illuminite Intrepid Commuter Pants.  What I appreciate is they have a mesh liner, which keeps them from sticking to your legs, they have zippers on the bottoms so you can take off/put on over shoes, and they are roomy and fit over whatever you are wearing at the time.    I use them to sit on when it is damp/wet, and to keep warm in camp when it is wet.  They are black, but covered with Illuminite reflectiveness.  When I wear these, I do not get wet, do not get chilled. Great wind-blocker pants, too.  https://illuminite.com/products/illuminite-mens-reflective-intrepid-waterproof-commuter-pant-black