The difference between plant and air temperature (PT–AT) is a good indicator of water stress. PT–AT for chickpea was negatively correlated to water deficit and air temperature and positively correlated to wind; for wheat, PT–AT was positively correlated to water deficit, air temperature and solar energy; for canola, PT–AT was not correlated to the environment. Chickpea maintained positive turgor at the expense of water content and therefore more water was available for transpirational cooling. Wheat maintained water content at the expense of turgor and therefore there was little water available for transpirational cooling. For canola, PT–AT was affected by parameters other than environment.