The Natural Calendar: May

Rhododendron bloom (Sikkim, Nepal and the Himalayas): the spring flowering moves up the mountains from April into May, with the lower forests first and higher shrubs later. Reliable window; the exact weeks depend on altitude and the year's weather.

Midnight sun (northern Scandinavia, Iceland, Alaska): the sun stops setting in the far north from around mid-May and continues into summer. Predictable by latitude; cloud can hide it.

High passes opening (Ladakh, Spiti, the Alps): snow clearance starts in late spring, and opening dates vary every year. Treat any date as a forecast.

Pre-monsoon heat (Indian plains and Southeast Asia): May is very hot, and thunderstorms build in the afternoons. Plan outdoor activity for early mornings; rains arrive in June in much of India.