The disturbances in the Bay of Bengal affecting Andhra Pradesh are generally rare between December and August, though the central coast may be affected in May and August once in five or six years. September to November are the principal months when the coast is much affected. On an average, at least one disturbance affects it in a year. During January, the atmospheric pressure is high in north India and it decreases towards the south. Over Andhra Pradesh, the pressure gradient is weak and is hardly one mb.
Winds are mostly light and are east to north-easternly.
Pressure decreases, and by March, it is nearly uniform over the State. Winds are light, easternly to south-easternly and get strengthened in the evening. In April, with the establishment of a low area over Bihar and its neighbourhood, a reversal in the pressure gradient occurs. The gradient over the State, however, continues to be weak. With the advancement of summer, the seasonal low over north India deepens and shifts towards the north-west.