The temperature during the Everest Base Camp trek can vary significantly based on the time of year and the altitude. During spring (March to May) the daytime temperature hovers around 17°C at lower altitudes, and 10°C as you climb higher. But it’ll drop in the nighttime to somewhere between -5°C to -10°C. Autumn (September to November) is similar. By winter (December to February) the temperatures will drop. Anticipate daytime temperatures ranging from just above freezing to around 10°C, and during the night temperatures can go as low as -10°C. Whatever time of year you visit, then, be sure to pack some warm clothes.