June 20th. – Summer Solstice-First Day of Summer
In Canada and the rest of the northern hemisphere, the first day of the summer season is the day of the year when the Sun is farthest north. This day is known as the Summer Solstice.
A solstice happens when the sun’s zenith is at its furthest point from the equator. On the June solstice, it reaches its northernmost point and the Earth’s North Pole tilts directly towards the sun, at about 23.4 degrees.
Although the June solstice marks the first day of astronomical summer, it’s more common to use meteorological definitions of seasons, making the solstice midsummer or midwinter.