Uzbekistan has an extreme continental climate. It is generally warmest in the south and coldest in the north. Temperatures in December average -8°C (18°F) in the north and 0°C (32 °F) in the south. However, extreme fluctuations can take temperatures as low as -35°C (-31°F). During the summer temperatures can reach 45°C (113°F) and above. Humidity is low.Spring (April to June) and Fall (September through October) are in general the most pleasant times to travel. In Fall it's harvest time, and the markets are full of fresh fruit. If you're interested in trekking, then summer (July and August) is the best time, because summers are almost dry.
