Cold weather can make easy things difficult. Starting your car requires warming it, if it snowed, cleaning the windshield and defrosting the ice. Put on layers and layers of clothes to protect from the harsh, cold winds. And pouring concrete becomes difficult.
Concrete can freeze before it can strengthen. It also sets more slowly, especially if the concrete itself registers under 50 degrees Fahrenheit. And under 40 degrees, the hydration reaction completely stops and the concrete does not set/strength.
As long as you are able to protect the concrete from cold weather before it is poured, it should be able to gain strength. If the psi is about 500 then it should be good to go.
In order to reach the 500 psi level, there are two things that can be done. Change the mix so it can set more quickly OR protect it from the cold. But by doing both, you can get it to 500 psi.
Having hot water ready to pour into the mixture will help.
Don’t use fly ash. Fly ash and slag cement set more slowly and generate less internal heat.
The slump should be at less than 4 inches and use air entrained concrete to reduce any bleeding.