Today we went to Gatineau Park for a little training hike, just 9.5 k from Champlain Lookout to Meech Lake and back.. It turned out to be training in the rain. So out came the rain jacket, back pack cover and we got to examine the interplay between the two. We were testing the "breathability" factor of rain gear ... while hiking uphill with 40 lb packs; that was rather aerobic.
What did I learn today?
The exertion that comes with lugging heavy packs keeps you warm - rain or not. The rain gear is great when it rains hard enough (it did!). If it's just a bit wet you are better off keeping the rain jacket off (ie maximum breathability) and just make sure you can change into dry clothes when done. Also, I was wearing a technical base layer that is designed to keep warm while wet - it worked.
Hiking boots (yes, boots, not shoes) are drying out now :) Backpack isn't since it stayed dry. All in all a fine experience.