Foraging activity of the red imported fire ant,Solenopsis invictaBuren, was monitored at bait traps for 1 yr to determine how weather and season affected foraging. Soil temperature at 2 cm was the best individual predictor of foraging rates at our study site (R2= 59%); workers foraged from 15 to 43°C, with maximal rates between 22 and 36°C. Season explained another 19% of sample variation in a multiple regression with soil temperature; this was because foraging was unusually low in late fall. Rain reduced foraging rates by ca. 40% and explained an additional 3% of the variation. Workers did not exhibit a tendency to forage more at night because neither time of day nor night/day were significantly correlated with foraging rates. Relative humidity, saturation deficits, soil moisture, and wind were also unrelated to foraging. Average weight of individual foragers increased ca. 30% with increasing soil temperature and decreased 15% with the advancing season. Soil-temperature data were used to calculate periods of foraging activity for an open pasture, a nearby shaded woodlot, and seven additional locations in the southeastern United States. Activity periods were distinctly shorter in shady habitats and higher latitudes. Low temperatures limited activity much more frequently than high temperatures.