Google announced an API for Google Trends at Search Central Live APAC 2025

Key features:

• 5-year rolling data window (with most recent data 48 hours old)
• Daily, weekly, monthly & yearly intervals
• Geographic breakdown: countries, regions, cities
• Consistent data scaling so you can get a better idea of search interest when you compare multiple searches (the GT website gives you a different 0-100 scale each time you run a search)
• Compare more than 5 search terms at once (GT website limits you to 5)

You can apply for access to Google Trends API Alpha - they're prioritizing developers with clear uses cases in mind, people who will start using it right away, and people willing to provide direct feedback.