Aestas ("summer", or "summer heat") is the Roman personification of summer. She is mentioned by Ovid in his Metamorphoses, and She may be his own invention. He describes Her as standing by the emerald throne of Phoebus (the Sun-god), with the other personifications of Time such as the Day, Month, Year, Century, and the Hours and the other Seasons, Spring, Autumn and Winter. She is naked except for a garland of grain or wheat-sheaves in Her hair.

According to Pliny the Elder, the Summer Solstice takes place when the Sun is in the eighth degree of Cancer. What the Romans thought of as the first day of Summer was considered to take place on the forty-eighth day after the vernal equinox, which Pliny states as the day when the Sun enters the 8th degree of Aries. (By modern figuring, the Sun enters the 1st degree of Aries on the vernal equinox). Using the current calendar, that puts the Romans' first day of Summer on the 7th of May. Silvius, though, considers the first day of Summer to be the 27th of June.

Ovid's depiction of Aestas may owe something to the Greek depiction of the Horai, the Goddesses of the Seasons. Their number varied with the place and time of their worship, there sometimes being two, three, or four of them, but they were generally shown as garlanded with the fruits or flowers of their respective seasons.