Russ J did not realize this post took an hour to compose (along with some interruptions), you had not posted when I started this, lol
Not a thermodynamics major, here is my contribution:
The gradient of temperature change is form high to low, so if the rig is warmer than the outside air temp it would loose heat (its warmth) to the atmosphere, until the current atmospheric condition (temperature) is attained. The wind factor affects the rate at which the heat (warmth) is lost.(the wind factor could cause freeze if current atmospheric conditions are 32F or below, let me explain)
"water freezes at 32F", thats a generic statement that we all use, but at 32F you could have a container of all water, or a combination of water and ice, or ice only. What determines the state or combination of states is the loss of waters latent heat, this is a heat loss that occurs without a change in temperature, and could bring the "pure water" to all ice at 32F.
Notice I mentioned "pure water", impurities in water (minerals, additives) affect the freezing point. Example,.. table salt will lower the freezing point, meaning the solution will freeze at a temp below 32F, at what temp?..... that depends on solution concentration (amount of salt in solution) anywhere from around 32F to 0.0F
All that being said,So if the air temp is below 32F with or without 60mph wind the water will freeze, what we dont know is the rate at which it will.(and I guess that what you are asking)
if temp is at 32F at 60mph it would freeze too, a little slower
Above 32F it would not freeze even at 120mph.
The reality is a lot of factors affect the answer, inlet water temp, the coil temp at drive start, the type and quantity of impurities in the water, the quantity of water, the coil insulation, machine insulation, etc
In my opinion, one hour drive time at 60 mph, even at 32 deg, would not freeze the system to cause damage, some components however may be frozen.... (exposed connections with little water).
You could fire up the rigs (3 mins) and attain working temps throughout the system for more safeguard, of course antifreeze of removing the water would be best.