The variations in temperature are also marked over the Indian sub-continent. During the winter seasons from November to February, due to the effect of continental winds over most of the country, the temperature decreases from South to North. The mean maximum temperature during the coldest months of December and January varies from 29 degree centigrade in some part of the peninsula to about 18 degree centigrade in the North, whereas the mean minimum varies from about 24 degree centigrade in the extreme South to below 5 degree centigrade in the North. From March to May is usually a period of continuous and rapid rise of temperature. The highest temperature occurs in North India, particularly in the desert regions of the North-West where the maximum may exceed 48 degree centigrade. With the advent of South West Monsoon in June, there is a rapid fall in the maximum temperature in the central portions of the country. The temperature is almost uniform over the area covering two thirds of the country which gets good rain. In August, there is a marked fall in temperature when the monsoon retreat from North India in September. In North-West India, in the month of November, the mean maximum temperature is below 38 degree centigrade and the mean minimum below 10 degree centigrade. In the extreme North, temperature drops below freezing point.