Karlovy Vary can be visited in the months of June to August as the weather is warm during this period and the tourists can enjoy all the outdoor activities.
Summer: June, July and August are warmest months and may result in storm and rains. This is a good season to visit Karlovy Vary and the tourists can expect crowds as this is a high season.
Autumn: Karlovy looks full of life as the leaves tend to change their color from bright green into yellow, orange and red during autumn season which lasts from September to November.
Winter: Winters span from December to February. During coldest months in Karlovy Vary, mountains are covered with heavy snow and temperature often drops below 2 degrees. Winter is when the locals take back the city and it is an off season.
So, the best time to visit Karlovy Vary is during the summer (June to August) when the temperatures are generally pleasantly warm.