With summer in full swing and the sun high in the sky, now is a good time for a reminder about preparing for hot weather when you visit the regional parks.

Especially for hikers, bicyclists and equestrians who explore the outback, the main thing is to keep hydrated. Park district emergency staff have recently treated a lot of heat exhaustion cases brought on by lack of water. Take along plenty of the liquid -- at least a quart per person, even more if you plan for a long trip. Once you're away from the trailheads and picnic areas, there isn't any drinking water source in most of the regional parks.

And be sure to occasionally drink the water you're carrying. Dehydration can creep up on you, even if you don't feel thirsty. Sunscreen is another must. There's nothing like sunburn to take the "great" out of the Great Outdoors. Wide-brimmed hats are a good idea, too.

And don't forget our four-footed friends. Dogs wear fur coats all the time. And they don't sweat to the extent that we do. They cool off mainly by panting. So they need lots of water on hot days. Pet supply stores sell portable drinking bowls, or you can just take along a gallon plastic bag. They weigh very little, and they work fine. Fill as needed from your supply.

One way of beating the heat is to visit the parks early in the morning or later in the afternoon instead of during the heat of the day. As a bonus, you're more likely to see wildlife at those times.

TILDEN: Snakes, turtles and other ectotherms will star in a program from 10 to 11 a.m. Sunday at Tilden Nature Area in Berkeley led by naturalist Trent Pearce.

Ectotherms are animals that rely on external sources of heat to control body temperature, unlike us "warm-blooded" humans. The program is free and open to all ages. Meet Trent at the Environmental Education Center, which is at the north end of Tilden's Central Park Drive. For information, call 510-544-2233.

Redwood: Back in the 19th century, the area including what is now Redwood Regional Park in Oakland was the scene of extensive logging to provide building materials for an expanding population.

Some of this history will come to life during a moderate 3.5-mile stroll on Saturday led by a naturalist. It's free of charge, family friendly, and dogs are allowed. Meet at Redwood Park's Skyline Gate on Skyline Boulevard a bit south of Pinehurst Road. For information, call 510-544-3187.

BRIONES: Briones Regional Park in central Contra Costa County will be the venue for a Women on Common Ground hike from 6 to 10:30 p.m. Aug. 10, led by naturalist Katie Colbert.

It's a 4-mile round-trip hike to the park's lagoons, including some stargazing along the way. Bring a trail dinner with something to share. Women on Common Ground is a series for women who enjoy the outdoors but have concerns for personal safety.

The Briones hike is free, but registration is required. Call 888-327-2757, select option 2, and refer to program 2925. For more information on the series, call 510-544-3243 or email kcolbert@ebparks.org.

Black Diamond: One person's trash is another's archaeological treasure. This is the case at Black Diamond Mines Regional Preserve in Antioch, where interesting artifacts have been unearthed at the site of the now-vanished mining town of Somersville.

Naturalist Eddie Willis will host a free program there from 11 a.m. to noon Sunday. After viewing a short PBS documentary, you can see some of the items discovered at the dig. Black Diamond Mines is located at the end of Somersville Road, five miles south of Highway 4 in Antioch. Meet Eddie at the Sidney Flat visitor center, which is in the cluster of buildings on the left just past the entrance kiosk. For information, call 888-327-2757, ext. 2750.

Millions of years ago, the Black Diamond Mines area was a shallow seabed. Tunnels dug by 19th century miners revealed some of this geologic history. Eddie will lead an excursion to see the underground beach and other features of the historic mines in a program from 9:30 a.m. to noon Aug. 11.

The program is for ages 7 and older. Registration is required, and there's a fee of $5 per person. For registration and information, call 888-327-2757. Select option 2 and refer to program 2962.

Big Break: You can become a citizen scientist at Big Break Regional Shoreline in Oakley. From 9 to 10 a.m. every Saturday and Sunday in August, you can help the naturalists test the Delta water. They check and record water quality changes that affect the ecosystem.

And from 8:30 to 9 a.m. Wednesday and Aug. 21, naturalists Mike Moran and Kevin Damstra welcome visitors for coffee and discussion of science and current events that are affecting the Delta. Bring your questions and a mug. The coffee is free. Big Break Visitor Center is located on Big Break Road off Main Street in Oakley. For information, call 888-327-2757, ext. 3050.

DEL VALLE: At Del Valle Regional Park on Del Valle Road south of Livermore, there are naturalist-led campfire programs every Saturday in August, and noncampers are welcome. Children must be accompanied by an adult.

The program Saturday is from 9 to 10 p.m. The other August programs are from 8:30 to 9:30 p.m. Park by the campground store. For information, call 510-544-3249.

There are also campfire programs from 8 to 9 p.m. every Saturday in August at Anthony Chabot Campground on Redwood Road between Oakland and Castro Valley, featuring games, songs, photos and stories. Again, noncampers are welcome. Dress warmly. For information, call 510-544-3187.

Ned MacKay writes a regular column about East Bay Regional Park District sites and activities. Email him at nedmackay@comcast.net.