An additional info about this requirement:
We are working on an Anomaly detection platform, where we will be able to compare the performance values against the seasonal average of the metric in last 4 weeks. This will be performed automatically without any configuration from your side. Currently it is enabled for our testing accounts only. Currently this feature is in the testing phase, once we have stable feature, we will open it up for the small set of customers.
Hopefully that should help in proper alerting for thresholds.