I run very hot when hiking and also run the Lowa Tibets, plus this year had probably 20 field days over 90 degrees and 10 over 100. I tested a lot of shirts and a few pants, to manage such heat, with very clear winners.
For me, running as hot as I do, the merino or merino blends were simply too hot regardless of weight. I fell in love with the ultralight,
Outdoor Research Echo Shirts and
Kuiu Tiburon Pants
TOPS:
Outdoor Research Echo shirts
Amazon.com : Outdoor Research Men's Echo L/S Zip Tee : Hiking Shirts : Clothing
www.amazon.com
I run LS half zip for sun and tick prevention
Permethrin treatment for ticks was a game changer
Super light shirt and held up pretty darn well even in some rough burn areas
(small tears will happen though so have to be careful)
Good price
Tan color which is nice in dry grassy hillsides I'm often in.
Marmot and ArcTeryx LS shirts were good and light, but not as light and airy as the OR.
BOTTOMS:
KUIU Tiburon
lets even slightest breeze through fabric for cooling and side zips are a must for all my pants now
unbelievably strong and durable for so thin
KUIU Kutana - like them but not as cool as the Tiburons. I'll wear them if extended cool and windy conditions at sunrise/sunset, but most of the late summer hunts I do have lows in upper 50's/low 60's so Tiburons were perfect.
Cheers!