That's because the temperature difference between Haikou and Sanya is really too big. Although Haikou and Sanya are only 300 kilometers apart, according to the forecast of the meteorological department, the temperature difference here is two to three degrees in summer and five to six degrees in winter. So keep warm in the morning and evening. In summer, the temperature difference between the two is not obvious, and many people don't feel it. So summer is very suitable for traveling to Hainan, but in winter, if you take a bus from Haikou to Sanya, many people will be eager to take off their clothes.

In winter, because of geographical reasons, the weather in Haikou is relatively wet and cold, and many people put on some coats to keep warm. Sanya, however, seems to be still in summer, and it is very comfortable to walk around in short sleeves.

Then what we want to explain is that the whole Hainan belongs to the tropical region. The annual temperature in Sanya is not lower than 19 degrees, and winter is also the most comfortable place in China. Spring in Haikou comes earlier, and it will be humid and sultry after autumn, which makes people feel uncomfortable. Therefore, it is necessary to wear a mask. Moreover, due to the expansion of cities and the development of tourism in recent years, there are more and more people and cars, and air and water pollution is becoming more and more serious. Therefore, it is necessary to carry a mask with you.

Haikou and Sanya, the former has been engaged in infrastructure construction in recent years, although the equipment is perfect and the transportation is convenient, but the negative impact is that all kinds of pollution in the city are coming up slowly and need to be solved by relevant departments. Sanya, not developed like Haikou, is still an old city. Although there is a lot of traffic, there is no room for expansion, so it is crowded. Of course, the treatment of some pollution is not perfect because of insufficient equipment. In addition, many people from other places come here all year round, and the air pollution will rise with more people, so many girls wearing masks will be seen on the street.