I usually go with the 3 strikes rules. if three medium warning signs are apparent, then I abort the trip. I have been averaging 8 trips per year for about 20 years. I have aborted 5 trips.
If there is a risk that I can mitigate or remedy, no problem. but a few small to medium risks that I'll have to take my chances... 1 may be. 2, hmm ok... but 3 ? I go home and learn from my mistake and come back another day.
If I am with a reliable buddy, comfort level go up, whereas solo increases the risk factor. New terrain versus one that I'm very familiar with in all weather.
One story I'll share with you.
Death Valley, Telescope Peak. in April. The desert floor was 100F. solo. I get up to the trailhead, perfect alpine weather. I could see the highest (Mt Whitney) and lowest (badwater) points. I was a mile away from the summit, walking the ridge, strong winds came out of nowhere, thought I was getting blown off the mountain, had to hug the ground fast. I see a fresh frozen dead mouse. weird. I get up go +30 minutes, another freak hail storm pelted me with golf balls. Then to make things weirder(er-er) a military helicopter comes out and hovers over me, I was wondering if I had misread the maps and somehow stumbled unto a gov base. Then two military jets get into a practice dog fight (Tom Cruise/Top Gun) over my head. At this mountain altitude, they seemed VERY close. it's still pelting me with hail golf balls and the winds were still strong. I could see the summit was covered in snow, probably melted into ice, I didn't have crampons, no buddy, and even though I signed the trail head register, no one knew where I was or was looking for me, also no cell phone coverage.
I made the tough decision to abort, because with strong winds, no crampons, no lifeline - 3 warning signs for me to abort. Live to climb another day. I turned back, all along being chased away by punishing hail.
Here's the punchline:
I run back downhill, make it to the car, then its clear perfect alpine weather again.
It was weird, something in the cosmos didn't want me on that mountain. and that frozen dead mouse weirded me out. This is April. 100F weather on the desert floor.
next time, I'll bring crampons for the summit, and plan to hide and wait out the hail storm, may be I won't get spooked by the jet fighters war games, although that was a mountain high buzz kill. Also wondered if I was inhaling that oh-so poisonous jet fuel.