Have you created any social media accounts for your app? You can use Twitter; FaceBook; WordPress; etc to promote your app.
Be sure to implement Apple's new API for requesting ratings and reviews. After I did this, I saw a significant increase in ratings and an increase in downloads.
Have you tried Apple's Search Ads? It costs some (after the initial $100 free offer ran out), but paid off for at least one iOS app with which I was involved.
Have had a super cool paid weather app on the App Store for 9 months now but sales going nowhere.
Does your weather app have any unique features or stand-out differences that no other weather app has or claims to have? If so, try testing keywords representing those unique features (in app update submissions and/or search ads).
If not, too many competitors have likely already completely carved out 100%+ of that space.
I have found the Apple search ads to be the best. Facebook ads are your next best bet. Unless you have a whole bunch of money burning a hole in your pocket do not use Google adwords. Also post info about your app in the "IOS apps" part of Macrumors forum. It's a great way to share what you're working on. I don't think that the YouTube reviews are that great. They typically do not spend enough time using to the app so the videos are very clumsy. I admire you for even trying to make money on an app. Personally I did it for the enjoyment.