@raustin is right also in the morning time is the best time to water, that’s when the plants stomatas are opening which means they will take on full advantage of the water, during mid-day it’s the hottest part of the day so the stomatas start closing, which then means it stops taking water and holds what water it has and uses it in the increments it needs.
When it’s hot that than comes down to evaporation pressure. The hotter it is the higher the evaporation pressure is, which means they will drink more water and uptake more nutrients as well as carbon dioxide. When it’s cooler the evaporation pressure is lower which means they will drink less and take nutrients in at a slower rate as well as take up carbon dioxide at a slower rate.
However I do disagree with @raustin about watering right before night, if watering, water atleast 5 hours prior to lights shutting off. This is because plants are more prone to getting diseases or fungus’s around the root system, also makes them more prone to getting powdery mildew. At all costs avoid watering right before night fall.
In flower is the most crucial time to avoid watering before the lights shut off because the plants are more suceptable to getting powdery mildew, always water when the lights come on or in midday never before night fall 
, duely noted stomatas are at their fullest potential and most use in the morning when lights come on
Hope this helps explain a little better as well as clarifies the watering information 
Happy growings