Hot weather concreting is defined by ACI as "one or a combination of the following conditions that tend to impair the quality of freshly mixed or hardened concrete by accelerating the rate of moisture loss and rate of cement hydration, or otherwise causing detrimental results 
1. High ambient temperature 
2. High concrete temperature 
3. Low relative humidity 
4. High wind speed 
Hot weather effect on concreting 
Increased water demand for required consistency. 
Rapid evaporation of mixing water. 
Rapid slump loss. 
Increased plastic shrinkage. 
Difficulty in control of entrained air. Possible "Cold joints".