There are lots of hiking opportunities east of the San Francisco Bay in Alameda County and Contra Costa County. Most of the trails and parks in the East Bay are owned by the East Bay Regional Parks District (EBRPD).
Although the East Bay is not among the best-known of the world's hiking destinations, it has many hiking trails because the East Bay Regional Parks District (EBRPD) has purchased significant portions of land in the region, turned them into regional parks, and created numerous trails in these parks. Some of the longest trails in the EBRPD are well over ten miles in length. The parks district is still trying to add new parks to its area, but this is becoming increasingly difficult due to the limited amount of rural areas not already owned by the East Bay Parks District, the rate of development, high property taxes if you own land, and high land prices.
If you are inland but are not far above sea level (for example, the Tri-Valley), you can expect daily highs in summer to be around and lows in summer to be around . In a heat wave, high temperatures can get as high as , which of course makes hiking impossible. In the same location, winter highs will be around , with low temperatures in December sometimes dropping below . At higher elevations in the same area, temperatures will be lower but still high: peaks such as Mount Diablo aren't nearly as high in elevation as they appear, so temperatures could be much higher than you expected. For hiking, the best months are October to May when temperatures are lower.
None of the East Bay reaches the Pacific Ocean itself, but a lot of it has coastlines along the San Francisco Bay, the San Pablo Bay, and the Sacramento Delta. However, there are no hiking opportunities at or very close to the coastline; the closest hiking opportunities to the milder San Francisco Bay shoreline are in the hills directly east of Oakland, Hayward, and Fremont. Temperatures at these hiking destinations are not as extreme as those experienced farther inland.
The East Bay region is quite easy to access by car because it is connected to several freeways and highways. I-580 enters the region from both the western and eastern sides and the I-680 enters the region from the northern and southern sides. (Both of these freeways usually have traffic jams during rush hours, however.) Once you leave the freeways numerous country roads that lead to the East Bay Regional Parks and trails.
There is a general pattern when driving to one of the local parks: on your way to them, you will usually take a fairly wide road in one of the East Bay cities, but will eventually find yourself on a country road that leads to some ranches and a staging area, where you can begin your hike. Most of the local parks do not have any grand entrances or fancy visitor centers—you come to hike and view the scenery.
Some of the parks require fees to enter, while others do not. Some parks will also provide passes for the local people, and these help the locals save money if they come to the park regularly.
Generally, you do not need permits to enter a park or enter a part of it; however, there are exceptions. For example, Brushy Peak Regional Preserve is largely open to the public; however, the area around the peak itself, where there are no trails, requires special permission to reach. To hike in Ohlone Regional Wilderness, you need a permit, which is easy to purchase at the main entrance to Del Valle Regional Park.
The EBRPD has divided the land it owns into several parks, similar to the way American federal and state governments divide up the land that they own into parks. The EBPRD parks vary in size, but practically all of them (excluding shoreline parks) have some sort of trail network with which hikers can create a hiking route that matches the distance they want to travel. Some park trail networks connect with the trail networks of a nearby regional park.
East Bay Regional Park trails are usually in networks with other trails, all of which are inside a particular East Bay Regional Park. This should make planning a hike in the East Bay relatively simple - you just need to get to a park, find one of the park maps, and plan a hike that matches the distance you want to do. Some parks have larger trail networks than others, with Briones Regional Park and Las Trampas Regional Park having more trails than Dublin Hills Regional Park, for example.
Most of the parks consist of grasslands, oak-covered areas, and a combination of shrubs and small trees called chaparral. The western part of the East Bay is more tree-covered than the eastern sections, which are closer to the Central Valley.
The general pattern of the landscapes in the American West, which is desert at low elevations and forested land in the mountains, is generally not the case in California and the East Bay is the same. However, those who are in the East Bay will notice that while some of the lower hills near the Altamont Pass are very desert-like, the higher mountain ranges like Mount Diablo and those around Del Valle have noticeably more trees than the lower hills.
Note that most of the photos of the hills in the area are deceptive: they are nearly all taken during wet period of winter or spring to capture the hills when the grass is green, making the area look lush. However, during much of the year (May to October at the least; March/April to December at the most), these hills are gold-colored because the grass has dried out, waiting for either a wildfire to burn them or the rainy season to begin in October to December.
Some of the cities in the East Bay have more trees than would be expected, and this presents the illusion that the area has a wetter climate than it really does. The trees in the cities are almost all kept alive by irrigation, and naturally (as in the times when the area was inhabited by only Native Americans) there would be far fewer trees in the areas that are now densely populated.
Many of the parks have picnic benches or other nice picnic spots, so you can make your hike enjoyable by bringing a picnic lunch with you. The exceptions to this recommendation are smaller parks, like Dublin Hills, where your hike will not be long enough that you need to bring your own lunch.
Generally, parks that are close to the cities (like Sycamore Grove Park) have plenty of picnic benches, while some of the wilder parks in the EBRPD have very few, if any, picnic benches and picnic areas. If you're in a park without many picnic benches, either go to a staging area or look for the picnic symbol on a map. (On EBRPD maps, the picnic symbol is like a picnic bench viewed from the side.)
Getting lost in parks with many trails can be quite easy. To avoid losing your way, you should take a map if you go to any of the EBRPD parks; the East Bay Regional Parks District produces maps of all of its park areas, along with maps of certain trails and particular regions of popular parks. Their maps are consistent in design and will help you not lose your way. EBRPD maps are on their website in a printable format, so you can print one before you go on your hike.
It is of course easier to lose your way in a woodland than a grassland. In most cases, woodlands will exist inside canyons and/or around creeks, so if you're lost in the woods near a creek, getting to a grassy area will make it easier to know where you are. (But also remember that you should stay on trails when possible.)
If you're lost, there's always the possibility that you have left park boundaries. This would be rare, since as long as you stay on the trails you will almost definitely still be in the park. However, East Bay parks often connect with other parks (for example, Los Vaqueros Watershed and Round Valley are connect), and if you don't see your location or trail on the map you may actually now in a different park altogether.
When you reach an intersection in basically any park in the East Bay, you'll come to a post that will tell which trail you're on and which trail you've reached. Therefore, if you are lost (but still in the park) and you reach a trail intersection, you will be able to spot the intersection on the map.
Mountain lions are the biggest safety issue, particularly in the more remote parks. If you encounter a mountain lion, stay courageous and try to scare it way by extending your arms and legs to look as large as possible, make a lot of noise, and throw sticks and stones. You can reduce your chances of encountering a mountain lion if you avoid hiking during the early morning and late evening and you stay on trails where more people will be hiking.
Another wildlife-related problem, particularly during the summer, is with the rattlesnakes that live in the country areas of the East Bay. If you stay on trails of decent width, stay close to the center of the paths, and watch where you are going, rattlesnakes are not as likely to cause problems because you will be more able to spot them. Also, keep in mind that not all of the snakes in the area are rattlesnakes: only the ones with rattlers at the back are rattlesnakes. However, as a general precaution, stay as far away as possible from all snakes in case you are near a rattlesnake.
While these two species can be a problem in any of the local parks, parks like Sycamore Grove will be safer than, for example, Ohlone Wilderness; however, even in Sycamore Grove the mountain lions and rattlesnakes can be a dangerous problem that becomes life-threatening occasionally when an encounter takes place.