Bhutan’s climate varies significantly with its diverse altitudes and, like much of Asia, is influenced by the monsoon. Western Bhutan, in particular, experiences heavy monsoon rains, which account for 60 to 90 percent of the region’s annual rainfall. The southern plains and foothills have a humid, subtropical climate, while the inner Himalayan valleys in the south and central regions are temperate. The northern regions, with the highest peaks, remain cold year-round, with snow capping the main summits.

Spring in Bhutan typically starts in early March and lasts until mid-April, bringing dry weather. Summer begins in mid-April with occasional showers and continues through the pre-monsoon rains in late June. The monsoon season lasts from late June to late September, with heavy rainfall from the southwest, but the weather is generally bright and sunny, with some early snowfalls at higher altitudes. From late November to March, winter sets in, bringing frost across much of the country and snow at elevations above 3,000 meters. The northeast winter monsoon brings strong winds through the high mountain passes, contributing to Bhutan’s name, Drukyul, or "Land of the Thunder Dragon" in Dzongkha.

During the day, temperatures are generally warm, but nights can be quite cool, with winter temperatures occasionally dipping below freezing. Monsoon showers are common in the summer months (especially July and August), and sometimes in spring and autumn. The most popular months for travel are March, April, May, September, October, and November, when you can expect mostly warm, sunny days and cool to cold nights. Rain or snow is rare during these months but is still possible.

Seasons in Bhutan are as follows:

• Spring: January – March
• Summer: April – June
• Autumn: July – September
• Winter: October – December

Average Temperature in Bhutan:

Temperatures while trekking: During treks at altitudes between 1,000 m and 3,500 m, daytime temperatures typically range in the high 20s°C, dropping to around 5°C at night. At higher altitudes, daytime temperatures hover around 20°C, but nighttime temperatures can drop as low as -10°C.

Rainfall: In Thimphu and Paro, rainfall averages about 25 mm per month from January to March. This increases to 50 mm in April and May, 75 mm in June, and peaks at 300 mm in August. Rainfall decreases to 125 mm in September, 75 mm in October, and 25 mm in November, with December receiving little to no rainfall (0 mm).