If you feel the wind pick up and you have to slow down to feel safe and stable it's time to stop and check the weather forcast, chances are at this point you are already close to 20 - 25 mph winds and gusting higher.
Another good place to start is to plan your trip which includes checking weather over the route you are taking and during the trip check the weather before leaving out for the day.
If you know you are headed into a storm and its several hundred miles off but moving at x mph in a certain direction a little simple math can tell you about where you'll possibly run into it and still be able to make some miles before shutting down and waiting for it to pass. Often the strongest winds are on the leading edge of the storm and after a few minutes when it passes you can take off after a nice break.
If you look in the mirrors and the trailer looks like it's leaning it's already too late and time to shut down.
For wind direction I watch the grass on the side of the highways, much easier to judge than watching trees.... in the southwest you need to watch the tumbleweed.
Listen to the sound of your TV cutting through the air, chances are you know what the roar sounds like when you are doing 80 mph on a nice day so if it sounds like you are going 80 and your only doing 55 there's a good chance you have a 25 mph head wind or quartering cross wind.
Any way you do it, it's up to you to make these decisions and not wait for somebody to tell you. When in doubt, stop, take a short break and check it out. Always best to err on the side of safety.