Editing Geography of Nepal (section)

===Seasons===
The year is divided into a wet season from June to September—as summer warmth over Inner Asia creates a low-pressure zone that draws in moist air from the Indian Ocean—and a dry season from October to June as cold temperatures in the vast interior create a high-pressure zone causing dry air to flow outward. April and May are months of intense water stress when cumulative effects of the long dry season are exacerbated by temperatures rising over {{convert|40|°C|°F}} in the tropical climate belt. Seasonal drought further intensifies in the [[Siwaliks]] hills consisting of poorly consolidated, coarse, permeable sediments that do not retain water, so hillsides are often covered with drought-tolerant scrub forest. In fact, much of Nepal's native vegetation adapted to withstand drought, but less so at higher elevations where cooler temperatures mean less water stress.

The summer [[Monsoon of South Asia|monsoon]] may be preceded by a buildup of thunderstorm activity that provides water for rice seedbeds. Sustained rain on average arrives in mid-June as rising temperatures over [[Inner Asia]] creates a low-pressure zone that draws in moist air from the Indian Ocean, but this can vary up to a month. Significant failure of monsoon rains historically meant drought and famine while above-normal rains still cause flooding and landslides with losses in human lives, farmland and buildings.

The monsoon also complicates transportation with roads and trails washing out while unpaved roads and airstrips may become unusable and cloud cover reduces safety margins for aviation. Rains diminish in September and generally end by mid-October, ushering in generally cool, clear, and dry weather, as well as the most relaxed and jovial period in Nepal. By this time, the harvest is completed and people are in a festive mood. The two largest and most important Hindu festivals—[[Dashain]] and [[Tihar (festival)|Tihar]] ([[Diwali|Dipawali]])—arrive during this period, about one month apart. The post-monsoon season lasts until about December.

After the post-monsoon comes the winter monsoon, a strong northeasterly flow marked by occasional, short rainfalls in the lowlands and plains and snowfalls in the high-altitude areas. In this season the Himalayas function as a barrier to cold air masses from Inner Asia, so southern Nepal and northern India have warmer winters than would otherwise be the case. April and May are dry and hot, especially below {{convert|1200|m|ft|-3|sp=us}} where afternoon temperatures may exceed {{convert|40|°C|°F}}.