high winds?

It depends on relative wind direction, gustiness, how fast you are going, TT side area, CG and loading, the amount of control in your hitch setup, weight and stiffness of your tow vehicle.

Moving trailers don't just blow over from wind pressure when moving, like they might standing still. The get started tipping, also swaying, from wind pressure, tipping relieves the pressure, they bounce back, repeat and oscillations start building, pretty quickly beyond your ability to do something about it.

If the hitch connection is strong enough, it might take the tow vehicle over too, but more often you simply lose control before that happens and have a roll over accident from leaving the road sideways or spinning.

I have family whose 26 foot lightweight TT was blown over in 35-40 mph winds, caught suddenly leaving a sheltered area of highway for an open one. You don't need 100 mph.

rhagfo wrote:
I would say more like 40mph to 60mph depending on the weight of the TT.

That steady velocity, plus gusting, plus any velocity added by the movement of the TT, plus any turbulence created by a passing big rig. Passing rigs can whip you around pretty good.

This was posted some years back: (I've never done the math)
If you want to calculate an estimate of how much wind speed is required to overturn your trailer, you can use

V = SQRT(W*b/{0.00666*l*(h-h2/2)*(h/2+h2/4)})

where
V = wind speed, mph
W = trailer weight, lbs
b = trailer width (tire center-center), ft
l = trailer length, ft
h = trailer height (from ground), ft
h2 = tire height, ft

I dont travel over 50 MPH in crosswinds 40 mph+. Drive to the next available place thats safe to stop and wait it out.

Here in Wyoming they'll issue high wind warnings and close freeways to high profile trailers a LONG ways short of 100 mph. I think it usually is in the 35-50mph range.

Those kind of crosswinds are enough to make steering a car a real job, let alone a trailer.

2oldman wrote:
At least 100mph.

I would say more like 40mph to 60mph depending on the weight of the TT. TT go over easier in winds than 5er, for two reasons.

1. There is more free twist distance in the ball hitch than in a 5th wheel hitch.
2. TT are typically much lighter than a 5er, so for sq. ft. of sidewall it takes less force to push over.

In Alberta on highway 2 and 22 the wind can really blow. 80-120+ km/h is not unusual. I have heard that there have been times when it can reach 180+ km/h. I have seen 18 wheelers on their sides in bunches up these roads.

If you keep going 100km/h (60 mph) and the wind is really blowing it takes less wind to blow you over, depending on the direction of the wind. Head wind is bad for gas milage but not troublesome otherwise, tail wind can increase milage but push you around a bit and a cross wind can blow you over. The effect of driving at speed plus the wind compounds the forces that can blow you over, if you slow down you reduce this force. It’s all physics, (F=M*A) a moving vehicle is accelerating and increase the forcing acting on it. A stopped vehicle would take a significant wind to blow over because the force is reduced.

I don’t know the exact speeds but if you ever feel the unit get wiggly, slow down!

Lived in So. Cal. for many years and traveled I-15 from San Bernadino to the High Desert.
High wind advisory for high profile vehicles were routinely issued when wind gusts of 45 mph (+) were expected.

Watched several tractor-trailer rigs (semis) over the years get turned on their sides when they ignored the advisories......the area around I-15 and Sierra Ave was notorious.

The real issue isn't being turned over but losing control of the trailer in high crosswinds. I was almost taken out once by a semi whose trailer was blown into my lane in strong winds.

At least 100mph.