New Delhi, May 28 -- This May is, thus far, the wettest in India in 125 years, the period for which India Meteorological Department (IMD) has published gridded data, which allows detailed analysis of rainfall. An HT analysis of this data shows that the month will end up as the third wettest May since 1901 even if there is no rain in the remaining four days. While the early arrival of the monsoon has aided this trend, frequent storms across the country even before monsoon's arrival are a big reason. According to IMD's gridded data - it gives average rain for grids or boxes bound by two latitudes and longitudes 0.25 degrees apart that can be aggregated to calculate average rain for India - India has received an average of 100.7 mm rain up to 8.30am on May 27. This is the highest rainfall for the first 27 days of May (rain for a particular date in IMD's data is rain in the 24 hours up to 8.30am on the date). To be sure, IMD's official report for the month may find a somewhat different rank because it does not aggregate the number for India from gridded data but directly from the data from weather stations. However, that is unlikely to change the broad trend. For example, the rain this May is 88.5% more than the 1971-2020 average of rain for the May 1-27 period. IMD considers the average for the 1971-2020 period as the Long Period Average (LPA) currently for tracking rain's performance. The LPA for the first 27 days of May is 53.4mm and that for the month in its entirety is 63.3mm. This means that India has already received more rain this month than it usually does by May 31. To be sure, there is some deviation from the LPA in most years. However, the deviation this year is far more unusual. This can be seen from the standard deviation - a measure of how much numbers feeding an average deviate from it - of total May rainfall, which is 13.4mm. The 100.7mm rain India has received so far is almost three standard deviations above the LPA for the entire month. For seasonal rain, IMD usually categorises rain more than one standard deviation above the LPA as "excess". The numbers above make it clear that this May is going to count as exceptionally rainy. Another way to look at this is by ranking May rain so far with rain for the full month of May in other years. This shows that May 2025 will be the third wettest even if India does not get any rain in the remaining four days. To rank as the wettest or second wettest May -- a record currently held by 2021 and 1990 -- India needs just 12.4mm or 7.6 mm rain, respectively. It is possible that India receives this amount of rain in the next four days. The reason for this is that the LPA for the last four days of May is 9.9mm with a standard deviation of 4.1mm. This means that May can end up as the wettest ever even with usual rain in the next four days. Then, IMD has already issued rain-related warnings for large parts of India for every day up to May 31. What is the reason behind May being very wet this year? The early arrival of the monsoon - it arrived on the Kerala coast on May 24, eight days earlier than usual - has helped but is not the only reason. For example, this May was unusually rainy even before the monsoon's arrival. Only five days recorded a deficit from the LPA up to May 23, and each day from May 17 to May 23 received rain more than double the LPA for those days. Moreover, while the monsoon has only covered peninsular and the north-eastern parts of India so far, there is a large surplus of rain even in the rest of the country. Almost two-thirds (62.8%) of the country's area has a surplus of 60% or more compared to the LPA, a threshold used by IMD to classify local rain as "large excess"; and another 10% of the country has a surplus of 20%-60%, classified as "excess" rain. Regions with deficit of 20% or more cover just 9% of the country's area. They are concentrated in western Bihar, eastern Uttar Pradesh, northern parts of Rajasthan, Himachal Pradesh, Jammu and Kashmir, Ladakh, Tripura, Manipur, Arunachal Pradesh, and eastern parts of Assam. (See map) Why has India been rainy despite monsoon some distance away for most of the country? Frequent storms of different kinds is the short answer, as HT explained on May 23. For example, parts of northern states received rain from frequent western disturbances, a storm originating west of India, usually in the Mediterranean region. In addition, day time heating in northern India led to air becoming warmer, which created low-pressure areas (often more than one in the country at the same time) conducive for attracting moisture. Moisture has been in abundant supply with hot sea surface temperatures on either side of the Indian subcontinent. It is these kinds of storms that have led to deaths in the plains, in places such as Delhi and Saharanpur, Jhansi, and Sonbhadra, all in Uttar Pradesh....