Summer is finally here. Early Wednesday morning, at 12:24 a.m. the summer solstice arrived, marking the time the sun’s rays are  directly overhead at the most northern part of the planet for the year.  Because our planet revolves around the sun and is tilted at angle, we experience the seasons.   The amount of light reaching the Earth changes most dramatically at the poles and the least amount at the Equator, where there is generally 12 hours of darkness and 12 hours of light.

Meteorologists start their summer on June 1st.  We use the warmest 90 days to mark the summer season. Astronomical summer begins on June 21st, about three weeks later.   This is what most of you consider summer as well.

The largest gap between sunrise and sunset occurs on the summer solstice. Technically, this year, the largest gap occurred on June 20th.  We will lose just under a second of daylight Wednesday as compared to Tuesday.  This is because the solstice occurred so early on the 21st.

The greatest amount of daylight occurs on the summer solstice.

The biggest misconception about the first day of summer is that it’s when the latest sunsets and earliest sunrises occur. But because of the way the Earth is shaped, its elliptical rotation and time zones, the earliest sunrise in the Portland area was back on June 14 and the latest sunset will be June 26.  What is also true about the first day of summer is that the sun is at its highest point in the sky.   Notice the angle of the sun at solar noon will start to decline late this week as we are now past the summer solstice.

The term ‘solstice’ comes from the Latin “solstitium,” meaning the stopping or standing still of the sun, and marks the first day of astronomical summer.  For me, the journey toward the “longest day of the year” has always been somewhat anticlimactic.  We spend six months watching the amount of daylight increase and when it finally arrives and we turn the corner toward less light, the kids are still in school and July 4th is still two weeks away.

Northern Maine has more daylight this time of year than in the south, it flips after the first day of autumn.

One thing that won’t reach a peak for a while are the temperatures.  Even though the amount of daylight reached its maximum Tuesday, the planet takes nearly five weeks to respond to all this added solar radiation. Not until the third week in July will our temperatures reach their maximums for the year.  That doesn’t mean it will be our hottest week, but on average it is.

The average maximum yearly temperatures are reached about a month after the summer solstice.

Follow Dave Epstein on Twitter @growingwisdom

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