How bad does weather have to be, to not be allowed to drive?
it is always your decision if you should drive or not. You need to decide how safe it is. You know how much experince you have, and how your car handles the conditions
That's up to the local authorities, who have the right to declare states of emergencies and order roads be closed to the public. You can be arrested if you are not authorized to be on the roads. Right now, we have a good six inches on the ground with the worst still to come. Here, that's essentially nothing. In many states, two or three inches sends everyone into a panic. The last time the roads were closed here was the big Nor'easter in 1993.
It's a matter of the road condition. When ice forms or there is whiteouts and it's an actual risk to driver's lives they shut the roads down.
No one with any sense goes out to drive in a snowstorm. You can't see, your tires don't get traction, and the other idiots on the rode are very likely to swerve into you.
A friend of mine drove home from his work at the post office in Fairbanks, Alaska one night. As he crossed some tracks his tires broke from the rims. The rubber had frozen. He had to sit with his car running until help could come along. If you can imagine how cold that is and how stupid an error it could have been for my friend. He may not have had a phone.
That depends on the gov't. to decide.
It's really a judgement call - if you don't have any experience driving in snow, then you should probably err on the side of caution (although if you can safely get the vehicle to a large parking lot without a lot of poles, curbs, or other obstructions, it can be a good chance to practice). If you live somewhere that it is going to snow a lot, you should invest in snow tires or chains. If you have a rear-wheel drive car/truck you should put some weight in the back (sandbags work well). I prefer a front-wheel drive car - because the weight of the engine is over the drive wheels. I've driven in the snow for years, and I've never gotten stuck, or been unable to get where I needed to go - even in some pretty nasty conditions (ice is worse than snow - and it usually melts a little during the day here, refreezes at night, then the next morning it's brutal). I'm fairly confident in my ability to drive in snow, but I don't get cocky about it - my main concern is other drivers, because it's also very hilly where I live, and I've seen people lose control. Going up large hills is tricky - I've watched people get halfway up, start sliding, and end up having to abort. I hit the hill going as fast as possible, and if I start to lose traction on ice, I will start to move the car to the edge of the road where the refrozen slush gives me extra traction.
When there are typhoon, snowstorm, hailstone, no one could drive out.
If the weather is really bad, I won't go out unless I really have to. Having said that, once I did have to get home at night when the weather was really bad and the police were about to shut down the road due to white-out conditions. The cop advised me not to go but since the road had not officially closed yet, I could still go. I did, followed by one more vehicle behind me. Basically that person just tailed me as we proceeded at a very slow pace ( speeding up to only maybe 20-25 km/h in spots when visibility cleared briefly ) but often had to come to a complete stop as the blowing snow appeared as an almost solid white wall ahead of the headlamps. It was a pretty tense driving situation.
Here in New Orleans, it's against the law to drive in flood waters. We don't have snow. Maybe you can't drive during a blizzard where you are.
Unless the car isn't yours, no one is going to stop you from driving, but the answer depends on how good the car is in snowy / icy conditions and the experience and competence of the driver.
if you can't see any farther than the hood of your car, you shouldn't be driving.
It is up to you! You may have a 4x4 with chains on the wheels. Only sometimes roads will be closed so that will be a problem. Or, more often, the road is blocked with other cars stuck in the snow.
Local authorities can close roads due to the roads being impassable, but usually this requires a major storm. A lot depends on your vehicle. My Honda Accord is not usable in 6 inches of snow, My 4 wheel drive Suburban can easily handle twice that amount
There is no weather where you are not "allowed" to drive. You can be advised not to drive, but no-one can stop you.