Where to Find and Catch Seviper
From Pokemon Go Wiki
Seviper are found and captured in Nest and Habitat locations.
Nests
Seviper Nests are locations that consistently spawn Seviper.
Habitats
Seviper Habitats are spawn locations where Seviper is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: