Hreflang for regions (like states and provinces) within a country

In short, no. The "Supported language/region codes" section of Google's hreflang guidelines is fairly unambiguous:

The value of the hreflang attribute identifies the language (in ISO 639-1 format) and optionally the region (in ISO 3166-1 Alpha 2 format) of an alternate URL.

The use of the word "region" there is perhaps confusing. ISO 3166-1 Alpha 2 codes denote countries1.

What you probably want to do is known as local SEO, which relies more on content and off-site optimisations to target search queries with local intent. It's beyond the scope of your question to cover that here.


1 To be really pedantic, even this is semantically troublesome. For instance, the constituent countries of the UK don't have their own codes, even though they are countries (not states or provinces).