Figure \ref{786634} shows how irrigation effects varied spatiotemporally with summer climate conditions (i.e., total precipitation and averaged max temperature of June, July, and August). Here we focus on irrigation effects on LST and EVI in July as they had the largest magnitude in the growing season. Results showed that from dry to wet conditions along the precipitation gradient, \(\Delta LST\) (r=0.24), \(\Delta EVI\) (r=-0.30) and \(\Delta Yield\) (r=-0.40) between irrigated and rainfed maize all reduced, suggesting a weakened irrigation effect (Figure \ref{786634}a-c). The weak irrigation effect under wet conditions is understandable, because there is much less need to supply additional water when precipitation is adequate. Irrigation will not benefit crop growth if it becomes excessive \cite{Payero_2008,Li_2019}. In contrast, irrigation effects were strengthened from cool to hot conditions along the temperature gradient, and \(\Delta LST\) (r=-0.50), \(\Delta EVI\) (r=0.55) and \(\Delta Yield\) (r=0.59) all had higher correlations with temperature than precipitation (Figure \ref{786634}d-e). Therefore, irrigation effects such as irrigation cooling were expected to be greater under drier or hotter conditions, including either dry and hot counties (spatially) or dry and hot years (temporally). These results also explain how the east-west transition in irrigation effect of Nebraska is connected to climate regime.
3.3 Quantify the contribution of cooling and water supply