I've written earlier about using technical clothes in the summer for more endurance and way more comfort besides getting fewer days with chafed skin. In cold weather staying dry is even more important. I had a six and a half hour test that made me slack on the Dutch Open 2009 production sorry. I used Reed Quantum Pertex (http://www.chillcheater.com) jacket which uses Nylon 6.6 material that is way thin fairly durable feeling totally wind proof at 13 MPH winds and didn't allow the mild rain showers in at 35F. It cost me 40 Euros at http://www.bearwater.fi. The same material is used by at least one other British manufacturer -Buffalo. Not to be confused with the US leather clothing manufacturer.
The jacket has a web pocket into which the jacket can be folded into. The size when folded fits into a large hand. Weight is just over one disc and it evaporated the sweat so fast that i wasn't wet at all and had to remove shirts not to get too hot. That left me with summer time upper body mobility and explosiveness basically. I was 13' short compared to summer with my best shots with Northman and Valk having an unusually good traction and run up distance. In short i've never had a jacket this great. My trousers from http://www.chevalier.se also breathe and costs nads but should last for years is great too but the jacket makes a larger difference in keeping you dry thus warm and comfortable. I had technical long johns and IIRC about 100 gram/square meter breathing Merino wool shirt underneath.
Usually i have red patches all over my torso now i had one. It is 9 degrees F warmer than the last session with my old jacket but this test lasted three hours longer.