The higher the altitude, the lower the temperature, so the season appears later than on land.
Here's a question: Why do the peach blossoms in Dalin Temple bloom later than those at the foot of the mountain?
From the meteorological point of view, there is only one answer, that is, "affected by the vertical difference of temperature." In other words, the peach blossoms in Dalin Temple bloom late because it is a "mountain climate". It describes that the temperature at high altitude in China is very low.