Interesting question, Josie (in Cincinnati).
Yes, my answer that follows suggests one likely warbler species you'll see on both the Left & Right Coast, (but read farther down the page after the "XX" symbol to learn more qualified details):
1. On the West Coast in n. California where I live in the SF Bay Area, it's typical to see a heavy influx of transient Yellow Warbler individuals from mid-August through as late as mid-October.
An excellent spot to see them near where I live in Novato (Marin Co.) is the San Rafael-based Las Gallinas Wildlife Ponds. (To find this birding venue, see:
2. As for the East Coast (and the Midwest), Yellow-rumped Warbler (Myrtle subspecies) is an easy answer to your question because it's the most common warbler in the fall to see AFTER the initial wave of earlier migrating warblers passes through much of the lower and upper Midwest and New England, mid-Atlantic, and southeast USA.
Moreover, by September in most of these aforementioned places, this amazingly prolific warbler species is ubiquitous.
Able to feed within every portion of a tree's profile (and, thus, in technical terms, able to exploit many micro-habitats via "resource partitioning), this warbler in the fall may challenge the patience of querying birders as every new viewing opportunity results in one Yellow-rumped Warbler after the next.
Frustrated birders want to see more than Yellow-rumps, of course, so as one more Yellow-rump after the next fills their bincocular views, you might hear them vent: "Another Yellow-rump? Another Butter Butt! " (its well known nickname).
But fear not, my warbler friends. Consider my fond memories of seeing a forest dominated by Yellow-rumps when I lived and birded in the Midwest and on the East Coast. Often, the influx of Yellow-rumps was accompanied by the first snap of cold on an autumn morning, with a backdrop of colorful autumn trees framing the appearance of other birds joining the Yellow-rumps.
Related, and in addition, note some populations of the neotropical-migrating Yellow-rumped Warbler persist into November (and beyond) throughout the Midwest, including the Upper Midwest and New England. During some years, this species may remain and survive the entire winter in the cold northern latitude of, say, southern Wisconsin...and, for this reason, it is occasionally reported by birders during Christmas Bird Counts in the Midwest and on the East Coast.
In recent years, this species has even been known to "over winter" throughout the non-breeding season in the the Midwest and East, especially if its favorite winter food sources are available (e.g., wax myrtle berries in the East, for example).
As for other common species you might see on the West Coast in fall in lieu of Yellow Warbler,
in my area of n. CA 20 miles north of San Francisco, Orange-crowned Warbler is often seen as dispersers and/or migrants.
Vagrant warbler sightings of so-called East Coast warbler species primarily happens from August through October on the Outer Point lighthouse area within Point Reyes National Seashore, a one-hour drive from my house and a spot, by the way, that I often bring birders who employ me as a Marin County birding guide.
East Coast warblers that are common in fall besides Yellow-rumped Warbler?
Palm Warbler is the next most common one and often associates with Yellow-rumps, especially in from mid- to late-fall.
Regards, Daniel Edelstein
(where my "Birding Tours" area provides details related to my all-day guided birding tours)