Due to differences in latitude and the marked variety in topographical relief, Vietnam's climate tends to vary considerably for each region. During the winter or dry season, extending roughly from November to April, the monsoon winds usually blow from the northeast along the Chinese coast and across the Gulf of Tonkin, picking up considerable moisture. The average annual temperature is generally higher in the plains than in the mountains, especially in southern Vietnam compared to the north. Temperatures vary less in the southern plains around Ho Chi Minh City and the Mekong Delta, ranging from between  over the year. In Hanoi and the surrounding areas of Red River Delta, the temperatures are much lower between . Seasonal variations in the mountains, plateaus, and the northernmost areas are much more dramatic, with temperatures varying from  in December and January to  in July and August. During winter, snow occasionally falls over the highest peaks of the far northern mountains near the Chinese border. Vietnam receives high rates of precipitation in the form of rainfall with an average amount from  to  during the monsoon seasons; this often causes flooding, especially in the cities with poor drainage systems. The country is also affected by tropical depressions, tropical storms and typhoons. Vietnam is one of the most vulnerable countries to climate change, with 55% of its population living in low-elevation coastal areas.