Bhutan has a wide range of temperature and climatic conditions. For instance, while Thimphu is chilly in the winter, Punakha can be hot. It is therefore advisable to dress in layers and peel of layers when required. Also, for protection against cold, layered clothing is better than one or two thick garments. Clothing should preferably be made from natural materials, which allow the body to breathe. Bring comfortable, well worn clothing, and plenty of underwear and socks. If traveling in the cold season, bring two sets of silk vests and long johns, as they are warm and dry quickly after washing. Since you will be doing a lot of walking and hiking in Bhutan, comfortable walking/hiking shoes and several pairs of socks is a must.
Winter, i.e. December, January and February: Winter in most valley’s in Bhutan is cold, especially in popular travel destinations like Thimphu, Paro, Phobjikha, Bumthang and Haa. Having said that, it is only cold after sundown and in the mornings. Daytime is warm under the winter sun. Do bring warm/down jackets, sweaters and cardigans, long johns or thermals on top of your regular wears.
Spring, i.e. March, April and May: Spring will warm during the day and chilly in the mornings and after sundown. During the day you will be dealing with a day temperature of 10-15 degree celsius in most part of Bhutan and a sweater over a layer or two of t-shirt or a thermal will be enough for the day, it will be safer to bring some winter clothing as well.
Summer, i.e. May, June and July: Summer is warm/hot during the day and a little chilly in the evenings and at night. But since you will also be doing some hiking in the mountains, you will need to bring at least one jacket and some sweaters to keep warm from the evening wind and for the higher altitudes. If it should fit, a rain jacket will be useful, incase it should rain in the middle of a hike. Most of the time, during the day, you will be able to operate in a t-shirt (to give you an idea of the temperature).
Autumn, i.e. September, October and November: Autumn is the best season to travel Bhutan. Not only is the weather warm and sunny with no or little rainfall, the autumn color adds a lot of charm to it. Multi day trekkers will need to bring clothes to beat the temperature in the mountains and it can go below zero. For those visiting to experience the culture and do short nature hikes, a jacket and some sweaters/cardigans may be useful for the evenings.
Dress modestly and respectfully for visits to monasteries, dzongs and other religious institutions. Remove hats, caps etc. before entering, and refrain from smoking on the premises.
The following is a fairly exhaustive list of what you should pack for your trip to Bhutan.
Items that may be of use while traveling in Bhutan: Small day pack; proper pouch to hold your travel documents, money, air tickets and other valuable items/documents; clothes as per season, a poncho or rain gear /or umbrella (June – September); sunglasses/spare glasses, comfortable walking shoes, pocket knife, hat, camera, films and accessories (including spare camera batteries)
These items may not be necessary but if you are keen on it: Insect repellent, hand cream, small sewing kit and safety pins, sun cream, lip salve, soluble aspirin, antiseptic cream, anti-histamine cream, anti-diarrhea pills, a preparation for the relief of sunburn, and any medication you take regularly, or might need to take for a periodically recurring condition, such as asthma. You will be taking more pictures than expected or necessary, so be sure to have good batteries that will last you a whole day or two. There are many dogs in settled areas. They sleep in the day and roam around at night. Bring earplugs if you think their barking might bother you. If you wear contact lenses, bring a pair of spectacles as well, as at high altitudes contact lenses can irritate the eyes.
Trekkers: In addition to the above, bring
Sleeping bag (if you prefer to bring your own) and thermarest, comfortable trekking boots which have already been broken in and plenty of socks, noting that woolen socks dry quicker than cotton ones, facecloth, soap, hair shampoo, cold water detergent; torch or flash light with spare batteries, mirror, scissors. Also bring a water bottle and zip locks plastic bags for packing clothing while on trek.