Havia temporadas regulares na história antiga, ainda mais antigas do que a Era de Heros. Escrever e gravar eram raros até então, e a maior parte do que sabemos a partir de então são lendas transmitidas pela história.
Os Maestros analisaram o assunto, mas não puderam concluir nada, pois não há informações suficientes do que há muito tempo ...
Though the Citadel has long sought to learn the manner by which it may predict the length and change of seasons, all efforts have been confounded. Septon Barth appeared to argue, in a fragmentary treatise, that the inconstancy of the seasons was a matter of magical art rather than trustworthy knowledge. Maester Nicol's The Measure of the Days—otherwise a laudable work containing much of use—seems influenced by this argument. Based upon his work on the movement of stars in the firmament, Nicol argues unconvincingly that the seasons might once have been of a regular length, determined solely by the way in which the globe faces the sun in its heavenly course. The notion behind it seems true enough—that the lengthening and shortening of days, if more regular, would have led to more regular seasons—but he could find no evidence that such was ever the case, beyond the most ancient of tales.
The World of Ice and Fire - Ancient History: The Long Night
Então, para responder à sua pergunta do título: As estações do ano podem ter duração normal de cada vez, mas antes da história gravada.