EXPLAINER
The world has faced its 12th consecutive month of historic heat, and this summer is on track to be among the hottest yet.
While summer has barely begun in the Northern Hemisphere, heat waves have already gripped many parts of the world, including the United States, Mexico, Europe, the Middle East and South Asia.
Extreme heat has caused more than a thousand deaths, urgent health warnings and school closures.
July is historically the hottest month of the year, with temperatures in parts of the Northern Hemisphere regularly exceeding 40 °C (104 °F).
According to the United Nations World Meteorological Organization (WMO), July 2023 was the warmest month on record, likely the warmest in at least the past 120,000 years, and this year is already on track to be one of the warmest on record.
Axial tilt and summer solstice.
The Earth is tilted 23.5 degrees on its axis as it orbits the Sun.
This results in varying amounts of sunlight at different times of the year, creating the changing of seasons.
Astronomical summer begins at the summer solstice, which is around June 20 or 21 in the Northern Hemisphere and around December 21 or 22 in the Southern Hemisphere.
This is the day when the sun reaches its highest point in the sky at noon, giving rise to the longest day and shortest night of the year.
The part of the Earth that receives the most direct sunlight is 23.5 degrees above the equator, known as the Tropic of Cancer.
This line passes through Mexico, Bahamas, Egypt, Saudi Arabia and India, among other countries, which contributes to very hot summers.
Summer in the northern hemisphere
Although half of the Earth's landmass experiences summer from June to September, approximately 90 percent of the world's population lives in the Northern Hemisphere, where these months coincide with more direct sunlight and longer daylight hours.
In the northernmost cities around the Arctic Circle, the sun does not set between the end of May and the end of July, in a phenomenon known as the midnight sun.
In contrast, during the winter months, these same places experience a polar night, where the sun remains below the horizon between late November and late January.
Why is the afternoon hotter than midday?
During the summer months, the soil absorbs more energy from the sun, which warms the surrounding air and produces warmer temperatures.
The delay between warming and release is known as seasonal delay.
The Earth's surface, especially large bodies of water like the oceans, which comprise 70 percent of the Earth's surface, needs time to absorb heat from the sun and subsequently release it.
This explains why the maximum temperature of the day occurs in the afternoon, not at midday, and why July, rather than June, typically records the highest average temperatures.
How to stay cool this summer
As summer temperatures soar in various regions around the world, with some even breaking all-time heat wave records, staying cool becomes crucial. Fortunately, there are effective methods to beat the heat, whether or not you have access to air conditioning.
Here are 10 tips to help minimize the risk of heat stroke:
