Tashkent's summer is fierce — July and August routinely sit at 35–40°C, with dust storms and almost no rain. Walking around mid-afternoon is unpleasant; locals retreat indoors and to the parks at dusk.
The shoulder seasons are the right time. April to early June is the best window: warm days, mild evenings, fruit trees in blossom, and the parks at their greenest. September to early November is the second-best choice, with cooler air and harvest food (melons, grapes, pomegranates) flooding the bazaars.
Winter (December to February) is cold — around freezing, sometimes with snow — but the city remains pleasant and the museums and metro are at their least crowded. The Navruz spring festival on 21 March is the major holiday; expect closures and festivities.