Wednesday, June 20, 2012

Does summer really start tonight?

The answer to that question is "Yes" -- sort of.

The summer solstice in the Northern Hemisphere is reached at 7:09 p.m. Eastern time Wednesday evening, and that's the official start of summer.

Today has the longest time of the year between sunrise and sunset -- 14 hours 31 minutes and 16 seconds in Charlotte. So in that way, June 20, 2012, really fits the description of summer's first day.

But in three ways, it won't seem like summer:

-- The earliest sunrise actually arrived earlier this month.

-- Meteorologists consider June 1 to be the start of summer.

-- Our average temperatures haven't reached their highest levels and won't until next month.

Here are the reasons for those seeming oddities:


Our earliest sunrise in Charlotte was 6:09 a.m., and it happened from June 4 through Wednesday. The earliest sunrise time arrived 16 days before the start of summer because of a phenomenon called "solar noon."

"Solar noon" is the time of day when the sun actually reaches the highest point in the sky, and it's not always at 12 noon. That's because of the earth's elliptical orbit and its 23-degree tilt. The "solar noon" is actually after noon at the start of summer. It'll be about 1 p.m. Wednesday in Charlotte.

That's why sunrise times start getting later shortly before summer begins, and sunset times don't get earlier until a few weeks after June 20. For example, sunset Wednesday in Charlotte is 8:41 p.m., but it'll be 8:42 p.m. from June 26-30 before it starts getting earlier again.

That time difference is even greater at latitudes farther north.

By the way, the same thing happens at the start of winter. Our earliest sunset, 5:11 p.m., happens Dec. 1-8. By the time winter starts Dec. 20, sunset is three minutes later. Sunrise is 7:27 a.m. on the first day of winter but slides back to 7:32 a.m. in early January before it starts getting earlier.


I've discussed this before. Meteorologists consider December-February to be winter, March-May as spring; June-August as summer, and September-November as fall. That is because, according to meteorologists, those timetables seem to coincide better with what we consider "winter," "spring," "summer" or "fall" weather.

So from a meteorological standpoint, summer started June 1. And autumn begins Sept. 1, although anyone who's spent even one year in Charlotte knows real autumn weather usually doesn't arrive until a lot later.


There is a lag in seasonal temperatures, because it takes a while for the atmosphere to heat up and cool down. Our coldest winter temperatures usually come in January. Our hottest temperatures typically are in July and August.

The average high and low temperatures for the first day of summer in Charlotte are 87 and 66 degrees. But our hottest average high is 89 degrees, from July 1-Aug. 5. And if you take it down to fractions, the hottest readings are usually in late July.  Our warmest average morning low, 68 degrees, is from July 2-Aug. 16.