Sorry for the long narrative post everyone. I could condense this into something more data-oriented, but I thought I should keep it experiential. Hope this helps someone.
GENERAL
Thorofare Shirt in desert tan. Tested on 6 dayhikes plus an overnighter in a wide range of weather, all in PA from 8/30 to 9/10. (Not bad living!) In most cases I wore the shirt next-to-skin, untucked, with the sleeves rolled up. I wore the Outdoor Research Sun Runner Hat and Cloudveil Rodeo Pants (10 oz, made from Inertia fabric, a thinnish stretchwoven). Other shirts used in similar situations: Railriders Eco Mesh Shirt (6.8 oz). Icebreaker 200 S/S & 260 L/S Shirts (7-9 oz). Patagonia Houdini (3.36 oz, modified) w/ fresh DWR. Montane Lite-Speed (5.5 oz) w/ DWR washed out. Until now Iāve used the Eco-Mesh shirt anytime temps were too hot for merino (for me most anything above 60°F in direct sun). The Eco-mesh isn't always ideal for temps that cool with wind and rain, but in hot dry conditions I've been really happy with it.
For all tests I carried a McHale Subpop (backpad removed) w/ 8-20 lbs. I kept the pack riding away from my back and adjusted the weight onto my hips to allow some airspace under the shoulder straps.
TESTING NOTES
6 long dayhikes (separate days):
82-90°F, moderate to very high humidity, direct sun, some winds depending on the day, some mosquito pressure, moderate pace. Towards 90°F the shirt did begin to feel a bit stuffy, slightly more than the Eco-Mesh in similar weather. I almost always kept the front unsnapped halfway. Later I pulled the front hem out from under my hipbelt, letting the front of the shirt billow out for increased airflow. I stayed very comfortable this way, but these adjustments were key. I managed to mitigate sweat very well, everywhere except the middle back where airflow was poorer. I get this with the Eco-Mesh too. In the Thorofare I think it was due to high humidity rather than temperature per se. Mesh pit panels probably wouldnāt have helped much since I was sweat-free under my arms (but this was with sleeves rolled up). A mesh panel in the middle of my back would have done the trick. I did appreciate the wind-resistance more on the drier, breezier days (thanks Captain Obvious!). On another note, the collar of the Thorofare seals up better under a headnet than the Eco-Mesh or a crew neck shirt.
Early morning hike / thunderstorm:
62-67°F, 94% humidity. The hike began at 5:30am with light drizzle, breeze and fog. I was exceptionally comfortable in just the Thorofare Shirt. The fabric shed drizzle ridiculously well for a āhot weather shirtā and still felt dry on the inside. Then the skies opened up with torrential rain, lightening, and 40mph winds at 60-66°F ambient air temp. I was in a wide open location and basically got a serious smackdown. I wore the shirt under a prototype silnylon rain cape. I rolled the sleeves down for warmth and to protect from the stinging rain. The forearms wetted out after a couple of minutes but I remained comfortable hiking at a brisk pace in extremely hard rain for 30 minutes or so. For the last 15 minutes of my hike I took off my rain cape and let myself get completely saturated head to toe. Iāll spare the predictable details of my dry test: this fabric dries wicked-fast.
Overnight trip / colder conditions:
48-70°F while hiking, high humidity, no rain and a bit of a breeze. At 48°F (no direct sun yet) I started out by throwing the Thorofare over the Icebreaker S/S shirt I slept in. I overheated before temps hit 50°F. This was at a moderate pace on easy terrain. In retrospect, I should have just started out with the Thorofare next-to-skin at 48°F, keeping the sleeves down and adding a powerstretch balaclava until I warmed up. Given that temperatures were only going to rise, I would have been perfectly comfortable. Then again, I prefer to keep my torso layers thin and supplement with headwear and gloves more often ā less taking off the backpack to fuss with layers. Contrary to what another poster suggested, worn next to skin there is no comparison between the Thorofare and a DWR windshirt. I couldnāt understand that criticism. The Thorofare is far more comfortable against bare skin at any temperature. The feel was fine to me when it was brand new, but if you hike in it for awhile and/or wash it, it will soften up noticeably.
IMPRESSIONS:
For something like a thru-hike on the PCT, CDT and at least the Northern AT, the Thorofare Shirt seems like an extremely useful piece of kit. It rivals the versatility of a windshirt over a range of temperatures warmer than those in which a merino+windshirt combo excels. If hiking temps are consistently above 50°F (wet or dry) a DWR windshirt is usually too stuffy for me. For 45-90°F in the mountains with the potential for variable weather, direct sun, bug pressure, and wind Iād lean towards the Thorofare over the Eco-Mesh Shirt for the versatility. Even 95°F dry heat should be decent for me in the Thorofare w/ all available ventilation adjustments. The Thorofare fabric is a stretchwoven however, so I would not expect total comfort at 100°F and intense humidity. (Comfort seems to suffer due to high humidity much more than due to temperature.) The keyword here is āversatilityā – the fabric doesn't exactly strike me as a specialist item 'optimized for hot weather'.
I might consider a large mesh panel in the middle of the back. That or mesh pit panels might help me keep the sleeves rolled down more often in intense sun too. With one or both of those mods I could safely retire my white Eco-Mesh Shirt for pirate-themed Halloween parties only.
Below 45°F or so I expect a merino+Thorofare combo (w/ hat and stretch balaclava when needed) to strike a workable balance between breathability and weather-resistance for hiking in drier conditions. I should be able to test this combo in the low 40s on 2-3 longer trips in the coming weeks. For wet weather or strong winds in colder weather I would still revert to a DWR windshirt though.
Overall the Thorofare looks to be a good all-around shirt for the majority of summer conditions I face or plan to face. So far I like it.