@BrianD Good news, that was in fact a defect with our weather providers software to be fixed today. Thanks again for reporting this issue!
Our API was able to confirm the issue you were experiencing. In researching, they found an issue with the ingestion of the data, making some entries to not be available to the API.
The team has corrected the core issue and is currently reimporting the precipitation data to ensure data integrity and that it is fully accessible via the API. It may take up to a couple more hours to fully reimport the precipitation summary data over the last few days.
I will provide another update once I have confirmed the data has been fully imported.
Additionally, the team is continuing to investigate the core cause and reviewing the potential addition of new automated QA checks and alerting, to prevent this type of issue with the precipitation/summary endpoint in the future.
Again, I will continue to provide updates as this issue is fully resolved.