||The objective of this paper is to present a method for estimating seasonally specific ambient population counts. The central assumption is that the variation in observed night-lights is a valid proxy for ambient population. Island populations are used for validation, where it is possible to derive estimates of ambient population from national statistics. The method is then applied to the whole of Greece. The validation shows a strong correlation amongst night-lights derived estimates and the reference dataset. Based on the proposed method, national maps are produced showing the month when seasonality is in its peak, the peak value during that month and the overall length of the season, in terms of how many months exceed a certain threshold. Different seasonality patterns are revealed. An advantage of the proposed method, compared to other contemporary approaches, is that it is based on public domain, global data.