The app is Clime Pro on iOS, they lock full access to Hurricane Milton data behind a $10 USD per week paywall.
If you’re in the area impacted by Milton, you can find publicly available resources at the National Hurricane Center’s website: National Hurricane Center
Sadly it’s not US-only. Weather.com sued the German Federal weather service for having their app free of charge available on both app stores. The federal constitutional court ruled in weather.coms favour as the federal service infringes upon the constitutional right of property and business. It is now (rather the time I payed) 3,49€ one-time payment for having something as an app that is already being payed for my taxes. Meanwhile the danish weather service, whose I app I frequently use even though it is in Danish, is free due to their constitution being more lenient towards state services (or more socialist should I say to rile some people up)