Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
aestīvo, āvi, ātum, 1, v. n. [aestivus], to spend or pass the summer in a place (like hiemo, to pass the winter; so in Gr. θερίζω and χειμάζω), Varr. R. R. 2, 1: mihi greges in Apuliā hibernabant, qui in Reatinibus montibus aestivabant, id. ib. 2, 2: intra saepem aestivant pastores opacam, Plin. 12, 5, 11, § 22; Suet. Galb. 4; id. Vesp. 24; Stat. S. 4, 4, 22.