It’s the longest day of year – get out and enjoy sunshine

Summer is officially here. The solstice occurred yesterday at 4:59 p.m. PDT, and today we will enjoy one of the longest days of the year with 16 hours of daylight.

Daylight hours are dependent on latitude, so that the farther north you go from the Tropic of Cancer, the more daylight hours you will have. Folks in Anchorage, Alaska, will enjoy about 19.5 hours of daylight today, while in Barrow it will be daylight for a full 24 hours. South of our region, sunny Los Angeles will receive about 14.5 hours, and hot, humid Houston will get about 14 hours.

At first it wouldn’t seem to make sense that our longer daylight hours would not translate into warmer weather than what folks experience in the South. Most people also know that the warmest temperatures of the season do not occur in late June, but arrive sometime in late July and early August.

The reason we are cooler than our southern counterparts has to do with the intensity of the sunlight, rather than the number of hours received. Go back to the old flashlight and globe experiment. Stand a few feet back from a globe and shine the light directly onto the Tropic of Cancer. You will see a bright spot there, with lower intensity light elsewhere on the globe. Have someone spin the globe and you will notice that the more northern latitudes stay lit longer – though the light will be dimmer.

On the summer solstice, the sun’s most direct rays are focused on the Tropic of Cancer at 23.5 degrees latitude, where the sun is directly overhead at noon. The sunlight gets more diffused and lower on the horizon the farther north you travel, though the number of daylight hours increase. Even 24 hours of sun, when it’s low on the horizon, does not bring a whole lot of warmth.

The dog days of summer usually arrive sometime in late July or August, even though daylight hours have been growing shorter for four to six weeks. This lag time is due to the nature of the energy balance of the Earth. Earth is constantly radiating heat away. The most pronounced heat loss occurs during clear nights in the winter. Earth also operates at a sun energy deficit from the fall to the spring, with more heat being lost, than is being replaced by the sun. By the time the summer solstice rolls around, there is still a lot of “catching up” to do as finally more heat energy is being received than is being lost, and the earth continues to warm up. Locally, average high temperatures peak in the mid to upper 80s, with average lows in the upper 50s, during the last week of July and the first week of August.

Outlook for the rest of the year

We should see more dry days than wet ones for the remainder of the month. High temperatures will be averaging a few degrees above normal with the possibility of a few scorching 90-plus degree days toward the end of the month.