Use (hidden) URL query parameters to re-use the email and password in the signup page?

Question

I have a NextJS app with a login page. If the user enters a email that is not linked to an existing account, I want to show a button to redirect the user to the signup page.

Ideally, I would like the email and password entered in the login page to be pre-filled in the signup page.

I currently show a link:

<Link
  href={{
    pathname: '/signup',
    query: {
      email,
      password
    },
  }}
  as={'/signup'}
  passHref
>
  Go to signup
</Link>

The entered email and password are in the query params, but thanks to the as='/signup' property, they don't show in the browser address bar.

In my signup page I can fetch them using:

const {
  query: {
    email,
    password
  }
} = useRouter()

I'm wondering if this is safe and a good practice, or if there is a better way?

[EDIT] Would it be safe to temporarily use sessionstorage?