Heading south from Luxor, the fertile, green Nile Valley narrows considerably and becomes more and more enclosed by the desert. The climate also changes and becomes increasingly desert-like, with mostly warm, dry days in winter (December to February) – with an average temperature of about 26°C during the day – but often surprisingly cold nights. Summer (June to August) days are dry but often very hot, with temperatures hovering between 38°C and 45°C, making it difficult to visit sights outdoors. At the height of summer, temperatures hardly seem to drop during the night.