The irrigation effect on the crop was manifested as the differences between rainfed and irrigated maize, which can be seen in individual counties and all county average (Figure \ref{699893}). In three individual counties selected to cover different climate conditions (dry, wet, and hot), irrigated crops had a significantly lower daytime LST and higher EVI than rainfed crops during most of the growing season, especially in July and August (Figure \ref{699893}a-f). The lower LST found in irrigated maize marked the presence of irrigation cooling. At night, the LST differences between irrigated and rainfed maize were almost indistinguishable (data not shown), suggesting irrigation cooling effect mainly occurs during the day. For this reason, irrigation effect at night was not included in the following analysis. 
The average irrigation effects for all counties showed similar seasonal variations as the three individual counties presented earlier (Figure \ref{699893}g,h). The differences between irrigated and rainfed maize were initially small at the early growing season but increased progressively until the peak growing season. The largest differences in LST were observed in July (-1.63°C), followed by August (-1.19°C). The same was true for EVI with the largest differences in July (0.10) and to a less extent in August (0.09). 

3.2 Spatial and temporal variations in irrigation effect