The best trekking pants will depend on the type of trekking you will be doing. You will need to consider the conditions in which you are likely to trek, as well as the general temperature of the region or regions through which you will trek. In just about all cases, you will want to choose trekking pants that are waterproof or water-resistant, and breathable to allow sweat to escape the pants. Lightweight trekking pants are a good choice if you will be hauling your own gear, though in snowy conditions, you will want to consider a high quality pair of snow pants.
Trekking can be a highly physical activity, which means the body is likely to sweat, sometimes profusely, during the trek. A good pair of trekking pants will be breathable, or able to allow moisture from sweat to escape the fabric used to make the pants. This keeps the skin dry, which means the skin will stay warmer in cold weather and more comfortable in warm weather. Synthetic materials specifically designed to wick moisture away from the skin may cost more than natural materials, though the investment will be well worth the extra comfort and body heat regulation.
Be sure the trekking pants you are considering are made from waterproof or water resistant materials that are fast-drying. In some regions, you will be likely to get wet, so choosing pants that can keep that moisture away from the skin can enhance comfort and your ability to regulate body temperature. If the pants do get wet, make sure you have chosen synthetic materials that will dry out quickly, or natural materials that will be warm even when wet. Most trekkers will wear the trekking pants for several days in a row, so it is important to be able to dry them out and stay warm and dry for several days.
Consider trekking pants with zip-off legs. These pants allow you to remove the lower portion of the pant legs, thereby making the pants into shorts. This is handy for trekkers who will be going through regions with temperature fluctuations, or for trekkers who tend to have large swings in body temperature during different levels of physical exertion. The lower pant legs can be stowed in a backpack and zipped back on should the weather change again, and in some cases, the pants will feature large cargo pockets in which the lower pant legs can be stored when not in use.
