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.
In recent years Uzbekistan was notably affected by the global warming and dry-out of the Aral Sea, which turned snowy cold winters to mild with less precipitation by allowing to travel in the wintertime. The following is the average temperatures in Tashkent, the capital of Uzbekistan.