Very generally speaking, a decision to bail will depend on your knowledge of the environment and conditions. I am pretty familiar with western US mountain and desert country, but totally ignorant of tropical rain forest. I would make a more informed decision in familiar country.

What equipment and skill sets are available to deal with foreseeable problems and challenges? If it going to snow,do we have snowshoes? warm clothing?

Urgency - How important is the objective? Must it be done right now? I have abandoned climbs in the face of threatening storms, knowing full well the rock would still be there on a more favorable day.

Basically, however, it comes down to a gut feeling that things are not going well. Discretion wins the day. I have seen too many situations where folks, probably driven by overwhelming egos, pushed on, with very bad consequences, leaving SAR to pick up the pieces....

As Montanero says, there are many variables involved, but these are at least some of the more significant.