Sareyn sits at around 1,650 metres and is busiest in summer, when Iranians escape the lowland heat. From June to September the days are mild (20–28°C) and the evenings cool enough to enjoy a hot bath after sunset. The Sabalan slopes are open for walking, and the nomad camps are in full swing.
Winter is a different town. Heavy snow closes the mountain road, and temperatures drop well below zero, but the springs steam dramatically against the cold and many Iranians consider this the most authentic time to come. Bring serious clothing if you visit between December and March.
The shoulder seasons in April–May and October are quietest, with cool but workable weather and the lowest hotel prices.