This summer has been the hottest in decades for the Indian national capital. The average maximum temperature in Delhi this year for May-June has been 41.57 degree Celsius, the highest since at least 1980, for which firm data is available.

As many as 49 of the 61 days in this two-month period saw the mercury soar past 40 degree C, another record for the past 33 years.

TOI analysed daily maximum temperature data since 1980 for Delhi's main weather station, Safdarjung. The data was taken from the US government's National Climatic Data Center(NCDC), which collates data from stations across the world.

Because of gaps in data availability, the years 1992, 1994 and 2005 have been excluded from the analysis. However, even for these years, the limited available data suggests shows that average was lower than this year. For the remaining years, NCDC has data for at least 55 of the total 61 days.

The data shows that in the last 33 years this is only the ninth time that the average maximum temperature for May-June has been above the 40-degree mark. By this measure, 1995 witnessed the second hottest summer with the maximum averaging 41.25 degree C. For the remaining seven years, the maximum averaged between 40 and 40.97 degree C.

Contrary to popular perception that there has been a general increase in summer temperatures in recent years, seven of the 13 years since 2000 have witnessed the mildest May and June in the past 33 years.

With the maximum temperature averaging 36.11 degree C, the mildest peak-summer was in 2008. Similarly 2011, 2006, 2000, 2004, 2007 and 2008 all witnessed a lower peak-summer mean. The average maximum temperature for these years was less than 39.91, the median for the 33 years under study.

It's of course not just the maximum temperature that makes your day scratchy. An otherwise pleasant week might have a couple of days when the mercury crosses 40 degree C and people generally don't complain. The real problem is when the 40-plus spell stretches for several days.

Even on this count, 2012 has been particularly bad. The number of 40-plus days this year has been the highest in these 33 years by a comfortable margin. In the ongoing summer, eight out of 10 days have seen the maximum cross this benchmark. While many have compared this summer to the one in 2010, that was the third hottest in the period since 1980 in terms of the average maximum. With 42 of the 60 days for which data is available registering 40-plus, it was the second most uncomfortable of the 33 years by that yardstick. The third worst year in this list is 1981 which had 40 such days.