As would be expected, the amount of water transpired varies significantly with the time of year. The average daily transpiration for the whole year amounts to 34.2 gallons (129 liters) per tree per day, with a range varying from 16 gallons (60 liters) per day in February, to 53 gallons (200 liters) for June. The change in the rates of transpiration is highly correlated with the air temperature (r = 0.834). (Walton B. Sinclair)

Millet

Vapor pressure deficit and wind speed are one of the best predictors of ET.

what is important is that Millet have shown the dramatic difference in water demand from late winter to mid-summer.

The actual demand will also depend on tree size, the land area it covers, its health and other factors. So what was the size of that grapefruit tree?