A park in the area (Riverside, CA), has a sign warning of rattlesnakes, but in the past 5 years I’ve lived here, this is the first time I’ve actually seen a snake. No rattle on it, though it was a pretty good size (several feet at least). Any ID help (and is it likely venomous)?
Gopher snake?
I have only seen little bitty Gopher Snakes, but apparently they do get quite large.
Here is a page on them. It does look like it could be a Gopher Snake.
Ask Crotalus - I believe he knows all the snake things.
If it’s not a rattlesnake, in California, it’s not likely to be poisonous, unless it’s an escaped pet.
It could be a king snake–though the markings do look more like a gopher snake. King snakes eat rattlers and want no part of a human. I suppose like any wild animal they might bite if startled, or if a pet went after them, but generally not a problem.
Looks like a gopher snake. Painful bite, and they can mimic rattling behavior, but harmless.
Gopher snake, in all likelihood. Harmless, if left alone. They can get big.
We had a gopher snake one that size in our back yard a few weeks ago. Landscaper said that they (like king snakes) eat rattlers and pack rats so they are beneficial.
More importantly they eat gophers :). They actually take very few snakes, the great bulk of their diet consists of small mammals, then birds and lizards in descending preference. Snakes are very incidental to their diet.
Kingsnakes on the other hand take a higher proportion of reptilian prey ( though they are also very much generalists ) and seem to have adpated specifically to taking them down.
I’m an easterner so I wanted to check and be sure snakes in the genus Pituophis are found in CA, since that’s what this appears to be. And indeed, there are representative species in that area. Whether they are locally called gopher, pine, or bull snakes these are large, powerful non-venomous constrictors that seem to specialize in preying upon burrowing mammals. The ‘gopher’ refers to ‘pocket gophers’ not the much larger groundhogs. If my friend Crotalus happens along, he may have additional insights.
We don’t have groundhogs out here - I never even knew anyone ever referred to them as ‘gophers.’ Learn something new every day ;).
But yep gopher snakes ( which I agree that certainly is ) are one of our commonest snakes in CA. Highly variable temperment by population, but frankly I’ve hardly ever had one try to bite me on being picked up.
Well, that’s really interesting. Our local version is called Florida pine snake and it’s pretty rare. But every single individual I’ve encountered in the wild and handled has done a vigorous blow and snort display that includes open mouth strikes. They’re big, chunky snakes and they strike with nearly half their body so the strike is avoidable. Nothing like the swift and superbly accurate strike of, say, an Amazon tree boa. But the pine snake could easily intimidate a first time handler! So I’m fascinated that your local version is so different. As you say, learn something new… 
Definitely a gopher snake…very common in California. Unless you pester it or try to pick it up there’s practically no chance of getting bitten by one. They are pretty docile if handled gently–I’ve seen them passed around at science programs to teach people about snakes.
This old paper ( just the abstract here , but I remember it from my old college days ) is a fascinating analysis of gopher snake color variation and its relation to potential rattlesnake mimicry in CA. In particular closer mimics seem to defend more aggressively to play up the facade of being a rattlesnake.
nitpick (but this is the dope after all)…it would be venomous rather than poisonous seeing as it would be a deliberate injection rather than passive ingestion or contact.
And one other little nugget of info, all snakes have venom glands to a greater or lesser extent, including constrictors but in those they have mostly been re-purposed to create a lubricating mucus but they still do contain something recognisable as venom.
But that’s a technicality really and to all practical human understanding, many snakes are not dangerously venomous.
Interesting! I’ve attempted to register with Researchgate to read the full text. Have to wait and see if I’m Researchgate material. 
Sorry to be so late to the party. Everyone else got it right without me. It’s a gopher snake. From my limited experience (three hikes in LA county), it’s the most commonly seen snake in southern California.
Ive seen several rattlers in Will Rogers State Park. Always keep alert and eyes on the trail when hiking.
Had a rattler literally crawl across my feet on a hike once, can’t remember the name of the park. My takeaway was that when you see signs warning you about snakes, go hike somewhere else.
I might agree for northern California, but what about garter snake? They tend to hang around humans more.
This is a distinction you are free to make in your own speech, but it is not a rule by which the corpus of english speakers abides.