Hi, and thanks for posting.
Short answer: history+ won't give you what you're after, because it contains historical weather simulations (a reanalysis-style archive), not an archive of the forecasts as they were originally issued. The Forecast API can return past forecasts via the history_days parameter, but only for the previous 4 days, so it isn't suitable for a 3-year comparison either.
A few useful things to know:
The history+ archive is built from weather simulations (NEMS, ERA5 and local high-resolution models), not from station measurements. It's a very good reference for "what the weather actually did" at a location, but it isn't raw observational data, and it isn't a record of what was forecast at the time.
For a true forecast-versus-observation study over multiple years, you'd need (a) an archive of the forecasts as issued on each day, and (b) a reference dataset to compare against (either station observations or a reanalysis like ERA5 from history+ or the Dataset API).
An archive of past forecasts going back years isn't part of the standard self-service offering. If this is for a specific project, the best route is to write to support@meteoblue.com with the locations, time range and variables you need. The team can advise on whether a custom dataset or a tailored verification extract is feasible.
If it would help, let us know a bit more about what you're trying to achieve (research, due diligence on forecast quality for a site, model selection, etc.) and we can point you at the most useful next step.
Best regards,
The meteoblue team