Tracking unseasonal temperature variations in cities around the globe and in India

Heatwaves in Europe, decade’s ‘coldest winter’ in Afghanistan, wildfires in Canada, and floods in India and China — the world has witnessed extreme weather events in 2023. Scientists and experts warn such extremes will continue to become more intense.

As countries grapple with the threats of climate change, we bring to you a daily tracker that lists cities in India and around the world which have been reeling under extreme weather.

The maps show cities experiencing either a warm spell or a cold spell, using temperature data collected from weather stations located at airports of these cities. If any place recorded unusually high temperature for six days in a row (three days in the case of India), it is said to be experiencing a warm spell. Similarly, if a city experienced a cooler-than-normal temperature, it is said to be under a cold spell, respectively.

The first section lists places around the world experiencing warm spells and cold spells, some of them potentially heat waves or cold waves. The next section identifies Indian cities that have been facing unseasonal temperatures, and the last section explains the method used to detect these climate change events.

Warm & Cold Spells Around The Globe

Isla Margarita in Venezuela, Ixtapa in Mexico, Zacapa in Guatemala are experiencing warm spells. Isla Margarita recorded a maximum temperature of 37.0°C yesterday, with its maximum temperatures over the last six days falling in the top 10% of all maximum temperatures for this period. This means that Isla Margarita is unusually warmer for this time of year.

Anaktuvuk Pass in United States, Tokat in Turkey, Ciudad Obregon in Mexico are experiencing cold spells. Anaktuvuk Pass recorded a minimum temperature of -31.0°C yesterday, with its minimum temperature over the last six days falling in the bottom 10% of all minimum temperatures for this period. This means that Anaktuvuk Pass is unusually cooler for this time of the year.

Warm & Cold Spells Across India

No Indian city is experiencing a cold spell or cold wave at present. Patna in Bihar is experiencing a warm spell. Patna saw a maximum temperature of 33.0°C yesterday. Mumbai in Maharashtra, Gaya in Bihar, Dibrugarh in Assam are not under warm spells, but they did witness unusually warmer temperatures yesterday. The max. temperature for Mumbai was 36.0°C.

The Method

To determine a warm spell or cold spell, we followed the methods of this project from the World Climate Research Programme.

The calculation involves recording the maximum and minimum temperature of cities around the world for the last few days. These are taken from automated weather stations at airports in these cities, stations that have been collecting such data for decades.

These temperatures are then compared with historical data from 1991 to 2020.

If a city's maximum temperature is regularly at the high end of the range for maximum temperatures for this time of year, it's in a warm spell. And if a city's minimum temperature is regularly at the bottom end of the range for minimum temperatures for this time of year, it's in a cold spell.

Sources: Iowa Environmental Mesonet for recent temperature data, NOAA Global Surface Summary of the Day for historical data.

Graphic: Shijith Kunhitty