J&K’s harshest climate is in Ladakh, with passes into the region open only between late June and late October, when the sun is at its strongest and the weather, at least during the day, pleasantly warm. Although it is officially a high-altitude desert, recent years have seen increasing bouts of rain in July and August, sometimes making trekking difficult. From November onwards, temperatures drop fast, often plummeting to minus 40°C between December and February, when the only way in and out of Zanskar is along the frozen surface of the river. Note that nearly all hotels and guesthouses are closed from some time in October until April, while many garden restaurants only open in the peak summer months.
Kashmir is at its best (though also at its busiest and most expensive) during late March and mid-May, when spring flowers abound, and from September to early November, with its golden days and chillier nights. Although the region’s climate is less harsh than Ladakh and the road up from Jammu kept open by the army, the winter months see some seriously subzero temperatures and heaps of snow. By contrast, as much of the Kashmir Valley (including Srinagar itself) is well under 2000m in altitude, high summer can be surprisingly hot, sometimes topping 35°C. It can also get quite wet in July and August.
Sitting at the top of the plains, the Jammu area can be visited at any time of year, though it can get extremely hot and humid between April and August and rather cold and foggy in the middle of winter.