Cold weather is defined by the American Concrete Institute as "a period when, for more than 3 consecutive days, the following conditions exist: 1) The average daily air temperature is less than 40° F and 2) The air temperature is not greater than 50°F for more than one-half of any 24-hour period."
The American Concrete Institute states that "hot weather is any combination of the following conditions that tend to impair the quality of freshly mixed or hardened concrete by accelerating the rate of mositure loss and rate of cement hydration, or otherwise resulting in detrimental results:
a. High ambient temperature
b. High concrete temperature
c. Low relative humidity
d. Wind velocity
e. Solar radiation