 Hot weather demands correct watering methods for plants and vegetables. A horticultural specialist with the Missouri University Extension Office in St. Genevieve County, Katie Kamler, says it's important to get the right amount each week. So hot temperatures lead to plants drying out really quick. And the rule of thumb for most of our fruits and vegetables that we would have in the garden, landscape plants also, would be they need an inch to an inch and a half of water per week.