Not sure about Canada fires, but everything else is just having the right gear. More layers, the right material, the right kind of gear, etc, makes the run 100% fine. I've been running 6 days out of each week for the past couple of months in NYC (including in storm/cold days; we've had shitty weather at down to ~15F) and I haven't missed a day due to weather reasons.

Some problems are harder and might require niche equipment. For example, if your roads are covered in ice, you need trail run shoes with spikes and a place where that can work, like dirt instead of asphalt. But those are the outliers.