These values are calculated from the daily weather data in 2014 at Holly Springs, Mississippi:

• the temperature-based growth potential for cool-season (C₃) grass, labeled here as gpC3
• the temperature-based growth potential for warm-season (C₄) grass, labeled here as gpC4
• the daily light integral (DLI) divided by the maximum possible DLI on that day, labeled here as dli_index

Each of the three values have been calculated for each day of 2014. That gives 365 values for gpC3, 365 for gpC4, and 365 for the dli_index.

These histograms, with the breakdown of what values were for these three calculations,  show why I say that variations in temperature affect growth more than variations in light.

For the DLI index, there are few values around 0, and many above 0.75. There are about 90 days for C₃, and more than 150 for C₄, with a growth potential of about 0.