Delhi has not yet crossed its normal August rainfall average, contrary to an earlier figure published by the India Meteorological Department (IMD). The weather agency has corrected the Capital’s cumulative rainfall total after identifying an erroneous entry in data recorded at the Safdarjung weather station on August 6.
With the correction, Delhi’s cumulative rainfall in August is 197.2 mm compared to 230.5 mm in the earlier figure of 230.5 mm. This means that the Capital received around 87 per cent of its normal August rainfall so far.
According to the IMD’s 1991-2020 long-period average, Safdarjung receives 226.8 mm of rainfall in August. Delhi is still about 29.6 mm short of its normal monthly rainfall average.
Incorrect August 6 entry caused Discrepancy
The discrepancy is related to rainfall data from 8.30 a.m. on 5 August to 8.30 a.m. on 6 August. The rainfall during this time was recorded as 56 mm in one of the tables on the IMD website.
The department has now corrected the figure to 18.7 mm.
The difference of 37.3 mm between the two figures led to the incorrect cumulative rainfall total of 230.5 mm. Once the error was corrected, the cumulative figure dropped to the correct 197.2 mm.
The correction also changes the earlier impression that Delhi had already received more than its normal rainfall for the entire month of August within the first eight days.
IMD explains how the error occurred
IMD Director Dr. Mrutyunjay Mohapatra said the discrepancy may be the result of an error during the recording of rainfall data.
IMD Scientist G D R Pattanaik visited the Safdarjung observatory, and he said the cumulative figure on the website had included the incorrect rainfall entry.
According to Pattanaik, the cumulative rainfall shown earlier was based on an entry of 56 mm instead of the correct 18.7 mm for August 6. The department changed the data, and 197.2 mm is now shown as the correct cumulative rainfall total.
Most importantly, the error was limited to a certain entry shown on the IMD website. Pattanaik said the figure issued in the daily Delhi weather bulletin remained correct, so the wrong value did not affect the rainfall figure reported in that bulletin.
Rainfall measurements at Safdarjung are recorded manually
The IMD senior scientist Krishna Mishra said rainfall and other meteorological observations at the Safdarjung station are manually measured and recorded.
He said once an incorrect value was entered into the system, it was picked up in the cumulative calculation. The higher rainfall total was shown.
The correction highlights the need for accurate data entry when calculating the cumulative weather statistics. Just one incorrect observation can change the total rainfall number and therefore can have a big impact on the total rainfall, especially if the data is used to determine if a city has crossed its monthly or seasonal average.
Delhi Still Needs 29.6 mm to Reach August Average
With the corrected figure of 197.2 mm, Delhi is still below its normal August rainfall of 226.8 mm.
As a result, the Capital needs approximately 29.6 mm more rainfall to reach its long-period August average.
The correction comes as Delhi is experiencing monsoon activity and rainfall is affecting temperatures, humidity, and overall weather conditions in the National Capital Region.
The updated IMD data offers a clearer picture of Delhi’s rainfall performance during the month. Rather than having already surpassed its August average, the Capital is currently at about 87 per cent of the normal monthly total.
The development also serves as a reminder that preliminary weather data can sometimes be revised when errors are detected. While rainfall observations are collected systematically, manual recording and subsequent data entry can occasionally lead to discrepancies that need to be identified and corrected.
For now, the official corrected figure for Safdarjung is 197.2 mm for August, and Delhi is 29.6 mm short of the normal August rainfall.
