If one forgets mashiv haru’ach u’morid hageshem (or gashem) and did not yet say v’ne’eman atta, it should be said where it is remembered.
If after that, but before baruch atta, say it and go back to v’ne’eman atta.
If after saying baruch, or baruch atta, (but not yet shem HaShem) go back to mashiv haru’ach in its regular place, and continue from there.
If Hashem’s Name was said (after baruch atta), we will assume in this e-mail that you say morid hatal every day in the summer, and in that case, just continue. And the same holds true for any time after that that you remember that you forgot.