I'm not sure how "ultralight" is defined for dayhiking, but shorts, shirt and no day pack is just plain UNPREPARED. There's no "ultralight" gear involved whatsoever. This nut should not be lumped in with responsible ultralight hikers and backpackers.
For backpacking, the common definition of "ultralight" is a base weight of 5-12 lbs of COMPLETE GEAR - all systems included - pack, shelter, sleep system, warm clothing, rain gear, first aid kit, toiletries, navigation, etc. A large percentage of thru-hikers on the PCT, JMT, CDT, and AT carry packs in this range or very near 12 lbs base weight. Food and water might double or triple that right after resupply. Cumulatively, they hike over a 100,000 miles each year between April and November in all kinds of conditions. Very few of them are rocket scientists or millionaires.
A backpacking base weight less than about 5 lbs is typically considered "Super Ultralight." These setups are usually extreme and probably dicey for adverse weather.
