The weather in Beijing is of the continental type, with cold and dry winters, due to the Siberian air masses that move southward across the Mongolian Plateau. The summers are hot owing to warm and humid monsoon winds from the southeast bringing Beijing most of its annual precipitation. January is the coldest month and July is the warmest. Winter usually begins towards the end of October. The summer months, June to August, are wet and hot with about 40% of the annual precipitation.
Beijing, the capital of the People's Republic of China is the nation's political, cultural, scientific and educational heart as well as a key transportation hub. Beijing has served as the capital of the country for more than 800 years dating back to the Yuan Dynasty.
Best season to visit Beijing: Summer (June to August) is considered peak season, when hotels typically raise their rates and the Great Wall nearly collapses under the weight of marching tourists. The autumn months between September and November have the best weather and fewer tourists. Spring is less pleasant - not many tourists but lots of wind and dust. In winter, you'll have Beijing to yourself and many hotels offer substantial discounts - just remember it's an ice box outside. Everything is chock-a-block during the Chinese New Year (usually in January or February).
Clothes for traveling: In autumn, jeans and a sweater are usually enough. In the warmer months, T-shirts and light pants or shorts are the best bet. In the colder months, it is wise to dress in layers: long underwear and jeans, shirt, sweater and down jacket. If you want to go local, you can buy a thick cotton army coat (jun da yi) for less than 100 yuan (12 bucks). Rain gear is necessary, especially during the summer months.
Avoid Peak Holidays: It is not a good idea to travel in China during Chinese holidays when it is the time Chinese people are traveling around. The most hottest three national holidays in China are Chinese Spring F estival (usu. in late Jan or early Feb.), International Labor Day (May1 to 7)and National Day(Oct 1 - 7). Spring Festival is an especially crowded time to travel. The advantage of being in China at this time is that you will get the opportunity to experience "first hand" the significance of these celebrations in Chinese culture.
Others Tips: An umbrella should be taken with in case the unexpected rainfall especially in summer. Sun glass and sun cream are needed to protect you from being hurt.