This map, created by climatologist Brian Brettschneider, represents the hours of sunshine in part of the northern hemisphere during the summer solstice, between 20 and 21 June.

To do this, the author uses a series of concentric red lines that pass through all the points that have an equal number of hours of sunshine on this day of the year. Thanks to this, we can see that Mexico City does not reach 13 and a half hours of sunshine, while Madrid exceeds 15 and a half hours, London 17 hours and Oslo 19 hours. On the other hand, Lapland, much of Greenland, northern Alaska, northern Iceland and northern Canada reach 24 hours, or in other words, midnight sun.

Sources

• Daylight-Twilight-Astronomical Maps