Don't concrete if rain, snow or frost is in the forecast. Click here for the weather forecast . Dark or black-colored concrete will be exposed to additional heat in sunny, dry conditions. Provide extra curing protection to prevent thermal cracking. Concrete made from the same supplier can cure to different colors if pour and curing takes place under different climates.
Temperature also affects the amount of water required to make the mix workable.
It takes less water at low temperatures to get a workable mix. Variations in water-cement ratio have a corresponding effect on concrete color. The shorter, the better. Specify the largest size of coarse aggregate usable to keep water content low. Get the supplier's assurance they are non-reactive.