Recent rains over much of the state are encouraging crop and weed growth and pesticide applications will be a primary focus as soon as fields are suitable. In a May 15, 2009 ICM News article, management factors to reduce drift potential were reviewed, with special focus on the effect of droplet size and wind speed on physical spray drift. As daily high temperatures increase into the upper 70 to 80s degrees F range, mid-day relative humidity frequently drops below 50 percent. This article takes a look at the effect of temperature and humidity on pesticide drift.