Summer heat peaks in inland San Diego

The Heat of Summer will most likely reach its feverish peak in inland San Diego County during the month of July. (Coastal San Diego is different: since its weather is greatly affected by the slowly warming mass of ocean water adjacent to it, coastal temperatures usually peak in August or September.) The weather station at Borrego Springs commonly measures midsummer highs in the 110s Fahrenheit (the record high is 122°, a reading set on June 25, 1990), but certain locales in the low-lying, barren basins of AnzaBorrego Desert State Park — notably the Borrego and Carrizo badlands — probably experience even higher temperatures. Overnight camping in the desert in summer is relatively carefree — little or no shelter is needed and early-morning temperatures are delightfully tepid. Prospective explorers of the desert in summer should take along enormous quantities of water and inform a responsible person of their whereabouts.

Grunion Runs in early July are most likely to occur after midnight on the holiday-weekend dates of July 4-6. This corresponds to 1-2 hours after highest nocturnal tide, 2-5 days after the date of the earlyJuly new moon. The small, silvery grunion tend to spawn on wide, gently sloping beaches such as Silver Strand, Mission Beach, Pacific Beach, La Jolla Shores, and Del Mar. California law allows the taking of grunion in summer by those possessing a state fishing license. The grunion must be caught by the hands only, and should be eaten (not wasted).

A Slender Crescent Moon briefly embellishes the western sky during the Independence Day evening twilight, stealing just a bit of attention from the fireworks displays. This and every July 4 is astronomically notable for the fact that it marks Earth's aphelion — the time when our planet lies farthest from the sun (94.5 million miles.) In January, Earth is an almost insignificant three percent closer to the sun than it is now. On account of this minor irregularity, Northern Hemisphere summers tend to be slightly cooler than they otherwise would be. At the same time, the Southern Hemisphere, which experiences winter during our “summer” months, has winters that tend to be slightly cooler.

With the advance of summer the Sagittarius Teapot, in the south-southeast lower left of Scorpius after dark, is starting to tilt and pour from its spout to the right. The Teapot will tilt farther and farther for the rest of the summer — or for much of the night if you stay out late.

Jupiter's Great Red Spot should be on the planet's central meridian around 11:45 p.m. tonight(July 8). Around that time Callisto and Ganymede are both at their farthest east of the planet, while Io and Europa are close in to Jupiter's west. There, Europa will disappear into eclipse by Jupiter's shadow around 12:39 a.m.

As twilight comes to its end, you'll now find the two brightest stars of summer, Vega and Arcturus, equally near the zenith: Vega toward the east, Arcturus toward the southwest (depending on your location). About a third of the way from Arcturus to Vega is the faint semicircle of Corona Borealis, the Northern Crown, with its one modestly bright crown jewel, Alphecca or Gemma, on its front. Nearly two thirds of the way from Arcturus to Vega is the Keystone of Hercules.

New Moon (July 9, exact at 6:17 p.m.)

The above comes from the Outdoors listings in the Reader compiled by Jerry Schad, author of Afoot & Afield in San Diego County. Schad died in 2011. Planet information from SkyandTelescope.org.