For South India, Pre Monsoon begins in March itself, unlike the north where Pre Monsoon only begins around April. In fact, for the southern parts, heat as well as thundershowers make an appearance during this time, making March to May, the Pre Monsoon months.
The intensity and frequency of Pre Monsoon activity only increases as months pass by with Kerala seeing the highest rains at 300 mm between March and May wherein March sees 30 mm, April 109.5 mm, and May 240 mm. During the second half of May, which is the waiting period for Monsoon rains in Kerala, Pre Monsoon showers pick up pace to quite an extent.
Tamil Nadu also sees good rains in the Pre Monsoon season at a good 128 mm while the state does not see rains in Monsoon, due to it being a rain shadow area. Pre Monsoon is fairly alright for Tamil Nadu with March seeing 18 mm of rains, April 42 mm, and May 68 mm.
This season has been disappointing so far with just North Interior Karnataka and Coastal Karnataka seeing surplus rains while rest of South India has remained deficient.
Kerala remains deficient by 70 percent, while Tamil Nadu saw even lesser rains with the state being 89 percent deficient.
Tamil Nadu and Kerala see rains in view of Wind discontinuity or Interior Peninsular trough from East or Central to the southern parts.
In the coming days, rainfall activity is all set to pick up over the southern parts mainly the states of Kerala and Tamil Nadu, as well as South Interior Karnataka.
A trough is running from Maharashtra across Rayalaseema to the southern tip.
Rains will start with Kerala today and will occur only during he later half of day due to Pre Monsoon showers.
Thereafter, the trough will shift to the eastern coast, and rains will also be seen over South Interior Karnataka as well as Tamil Nadu.
For the next four to five days, these showers of varied intensity will continue over many parts. In fact, the cities of Bengaluru and Chennai will also see some rainfall.
Please Note: Any information picked from here must be attributed to skymetweather.com