Plenty of rainy days, but not much rain: Where July stood in Delhi's 125 years of weather data

At least some part of the city received rain on 23 of the 31 days this month, making it the ‘22nd rainiest July month’ since 1901

July 2025 may not go down as a particularly wet month for Delhi in terms of rainfall volume, but it stands out for how often it rained. At least some part of the city received rain on 23 of the 31 days this month, making it the “22nd rainiest July month” since 1901 in terms of rainy days, according to gridded data from the India Meteorological Department (IMD) analysed by Hindustan Times.

Despite the high frequency of rain, the total rainfall this July has been relatively modest. Between July 1 and 30, Delhi recorded 150.5mm of rain — ranking 69th highest (or 57th lowest) for the month since 1901. (PTI)

To be sure, 1901 is the first year for which IMD has published a gridded data set.

While the gridded data for July 31 will become available only in the afternoon of July 31, it is expected to record rain, since IMD’s daily data corresponds to the 24-hour period ending 08.30am. That means showers seen after 08.30am on July 30 will be counted toward July 31 — effectively confirming 23 days of rain this month.

Total rainfall modest, though

Despite the high frequency of rain, the total rainfall this July has been relatively modest. Between July 1 and 30, Delhi recorded 150.5mm of rain — ranking 69th highest (or 57th lowest) for the month since 1901. The volume, therefore, doesn’t match the rank suggested by the number of rain days.

How unusual is this mismatch? A comparison with the long period average (LPA) — a baseline climatology from 1971–2020 — offers clarity. While Delhi received 14% less rainfall than the LPA for July’s first 30 days, the number of rainy days was 19% (3.7 days) more than the LPA average of 19.3 rain days for the month.

But even a 19% rise in rain days doesn’t appear dramatic enough to explain a 22nd rank. That’s partly because July has historically been one of Delhi’s rainier months — second only to August — so high rain day counts are more common. Additionally, rankings can move quickly when several years are tied. For instance, 2025 shares its 22nd rank with six other years that also saw 23 rain days. Consequently, years with 22 rain days are pushed further down to rank 29.

Another factor is the change in rainfall patterns over time. If the LPA were calculated using an earlier baseline — such as 1901–1950 — this July’s rain-day count would show a larger 26.2% increase over the average for that period, making this year seem more exceptional.

One city, many numbers

The patterns and conclusions also change depending on which data set you look at. One of the most widely cited is the data from the Safdarjung weather station — the oldest in the city. This station recorded 220.1mm of rainfall till July 30, which is already above the July LPA of 195.8mm for that location. However, this is only the ninth highest July total since 2011, which is the earliest year for which public data is available.

In terms of frequency, Safdarjung reported rain on 21 days this July — second only to the 22 rainy days recorded in July 2016. However, the IMD’s classification counts only 13 of those as “rainy days”, since the term is technically reserved for days with at least 2.5 mm of rainfall.

Explaining the mismatch

So why does the IMD’s gridded data show a lower volume of rainfall citywide, even as Safdarjung logged a high total?

The likely answer lies in Delhi’s hyper-local rainfall patterns. For instance, on July 30 alone, daily rainfall varied widely across the city — from 128.8mm at Ridge station to just 1.5mm at Najafgarh. The gridded data set accounts for such variability by averaging data across stations located within grid boxes bound by two latitudes and two longitudes 0.25° apart. For this analysis, the average rainfall across two such grid boxes covering Delhi was used.

In short, Delhi saw many damp days this July — but not necessarily heavy ones. It rained often, but lightly, making this month a statistical outlier in a different way: a month defined not by deluge, but by drizzle.