Lewis & Short

ārĭtūdo, ĭnis, f. [aridus], dryness, aridity, drought (ante-class.): ariditas, Enn. ap. Varr. L. L. 5, § 60 Müll. (Epicharm. v. 2 Vahl. p. 167); Plaut. Rud. 2, 6, 40; also in Non. p. 71, 21; Varr. R. R. 1, 12, 3.