At Deer Flat and Meridian Ridge at Mount Diablo, it can feel like miles of the lower delta are within grasp of your outstretched arms. On Bob Walker Ridge at Morgan Territory, you get a spectacular view of Los Vaqueros Reservoir watershed, Round Valley and beyond to the San Joaquin Valley to the east.

Of dozens of loop hikes in the Bay Area, these are four of my favorites. The key, of course, is this: On a loop trail, you never repeat a single step.

The timing couldn't be better. In the past week, the Bay Area has received some of its best weather of the year, with sparkling clear air and warm afternoons.

Drought? Maybe later.

But the payoff this week is spectacular weather, views and outstanding trail conditions.

Marin

Carson Falls Loop, 7.4 miles, Marin Watershed: This trip features gorgeous pool-and-drop falls (if it ever rains - it doesn't take much to recharge the falls), a secluded valley and pretty views of Alpine Lake and Mount Tamalpais.

The trailhead/staging area is on Bolinas-Fairfax Road Park at a service road marked by a green gate and billboard. Park your car just across the road at a pull-out on the shoulder. Start by hiking up the hill on Pine Mountain Fire Road, where you climb about 300 feet for a mile to Oat Hill Road. On the way up, turn back occasionally for views of Alpine Lake and Mount Tam.

Turn left at Oat Hill Road and walk about five minutes to the cutoff trail on the right near the power lines. Take that trail. It leads down into a valley to a small creek just above Carson Falls. Cross the creek and the trail will lead you to the midway point at the falls. Even at a trickle, Carson Falls is very pretty, where you can look up and see three waterfalls and a cascade as the creek pours through a basalt gorge.

It's 1.5 miles to Carson Falls. From here, take the trail down the canyon, a gorgeous, "secret" kind of place, to Kent Pump Road. Turn left and go 1.4 miles to Old Vee Road, then turn left again and climb 1.2 miles back up to Oat Hill Road. You complete the loop by returning via Pine Mountain Road. This is excellent, dry or wet.

Info: Free. Parking fills on Sundays. Dogs OK. Bikes permitted on fire roads. (415) 945-1195, marinwater.org.

S.F. Peninsula

Harkins Ridge/Whittemore Gulch Loop, 6.5 miles, Purisima Creek Redwoods Open Space Preserve: This is a dramatic trek that features redwood forest, fern grottoes, and the ridge-line views of the ocean and Half Moon Bay and beyond to the Farallon Islands. The best trailhead is at the Higgins Road staging area just south of Half Moon Bay. If the small parking area is full, park along the road's shoulder on the west side.

Start the trip by taking Harkins Ridge Trail. It passes under a redwood canopy and rises up a canyon into the coastal foothills. Eventually you climb, with a few steep spots, to Harkins Ridge, with valleys plunging below on each side. You climb about 1,600 feet to Skyline, with glimpses to the northwest of Pillar Point Harbor, about 10 miles away. Near the top, you turn left on North Ridge Trail, another left on Whittemore Gulch Trail and sail downhill back to the bottom. You seem to glide all the way, enjoy more views of the harbor, and the plunging into another canyon filled with redwoods, and a small creek trickling downhill.

Info: Free. No dogs. Bikes OK on Harkins. Winter bike closure (signed) on Whittemore (even though we saw several Saturday). (650) 691-1200; openspace.org.

Contra Costa

Mitchell Canyon Loop, 8.1 miles, Mount Diablo State Park: A 1,600-foot climb through a pretty canyon leads to a sub-ridge on the flank of Mount Diablo that provides long-distance views across the lower delta.

The trailhead is at the foot of Mitchell Canyon near Clayton. The trip starts with a steady two-mile climb up the canyon, and then it gets steep, rising 1,000 feet in a mile, to reach Deer Flat. If you wear cotton, pack an extra shirt and change out of your sweat-soaked shirt here and enjoy your view. It's been so clear this week that you can see Mount St. Helena in Sonoma County.

At Deer Flat, turn left and head to Meridian Ridge (a fire road), and keep on to a major road/trail junction at Murchio Gap. There are several ways to return to make it a loop, but I believe the best is to take the Back Trail and head downhill into a canyon to the Coulter Pine Trail. Turn left here and it's a short distance to the Mitchell Canyon staging area.

Info: $5. No dogs. Bikes OK on fire roads. (925) 837-2525 (recorded information), (925) 837-0904 (ranger kiosk); weather conditions at summit, (925) 838-9225; Mt. Diablo Interpretive Association, (925) 927-7222, www.mdia.org.

Alameda County

Bob Walker Ridge Loop, 5.7 miles, Morgan Territory: This is an easy hike that leads to a ridge-top spine that overlooks Round Valley, Los Vaqueros Reservoir and the San Joaquin Valley, with Mount Diablo looming off to the northwest.

The parking area and trailhead is at 1,900 feet, which takes most of the climb out of the hike. You start on the Volvon Trail for a half mile, climbing about 100 feet over a short hill and then on to a junction with the Blue Oak Trail. Turn left and hike 1.3 miles to the Valley View Trail (turn right), and then head onward and take the Loop Trail to Bob Walker Ridge. You emerge from rolling foothills, valleys and sub-ridges sprinkled with oak for the payoff views. The air was so clear this week that off to the distant east, you could see the snow-covered crest of the Sierra Nevada.

The loop trail circles Bob Walker Ridge. To return, continue ahead on the short loop trail to where it junctions with the Volvon Trail. Here the Volvon Trail runs all the way back to the trailhead (though a shortcut back to the parking lot is available by turning right on the Condor Trail). A favorite.

Info: Free. Dogs OK. Bikes OK on service roads. Map/brochure available for free at trailhead; (888) 327-2757, ext. 2, then ext. 1; or download PDF-file map at ebparks.org. (925) 757-2620 (c/o Black Diamond Mines Regional Preserve).

Tom Stienstra's Outdoors Report can be heard Saturdays on KCBS (740 AM) and FM 106.9 at 7:35 a.m., 9:35 a.m. and 12:35 p.m. E-mail Tom Stienstra at tstienstra@sfchronicle.com.

This article appeared on page D - 7 of the San Francisco Chronicle