It is cold, below freezing today and my husband wants the truck in the garage. If we aren't driving truck on the cold day, does it matter? He thinks the antifreeze may not have been strong enough for the weather here, as it was changed in a more warm state. Tomorrow will be above 40° .
Ice doesn't cause problems in itself, so long as you don't try to drive the car when the coolant can't circulate.
The problem with ice is that it occupies more volume than water, and if there is nowhere for the unfrozen water to get out of the way, the pressure is enough to break things.
Any reasonable concentration of antifreeze freezes gradually into a "mush" of solid and liquid, which can "flow" enough to equalize the pressure, and the radiator cap will blow to release the pressure before it gets high enough to damage anything.
So unless there was no antifreeze at all in the cooling system, you often get away with a car "freezing" gradually and thawing out naturally (i.e. not running the engine until it has thawed).
Anti-freeze is more accurately called coolant and as such is generally manufactured to provide protection from overheating, corrosion and of course, freezing. If properly mixed/installed, the protection from freezing will not be region specific.
Not driving the vehicle is a minor consideration. One can drive the vehicle to keep the coolant warm, but eventually you have to turn it off and it will cool to ambient temperature.
There are testing resources available. It's likely your local auto parts store will provide for you a testing of the coolant to determine the low temperature value that it can provide.
If water has been added to the system since the previous coolant replacement, the protection level will be reduced. There is no advantage to add more coolant to increase the percentage of protection, as the lower limit will not change appreciably. According to itstillruns, a ratio of 50:50 is typical, while the site recommends 70 percent anti-freeze to 30 percent water for extreme temperatures (like the arctic!) while recommending to keep the portion of anti-freeze above 40 percent.
Equally useful is the recommendation to consult the owner's manual for manufacturer's recommendation.
The coolant for a vehicle is specific to the vehicle itself, and is not normally changed to fit the area that the vehicle is serviced. If the coolant is new enough to not need service, it should quite easily withstand temperatures as low as -35 degrees fahrenheit.(37 degrees celsius.) If you truly want to prove either side, coolant testers are very cheap, and very easy to use.