CLI command to show status of an AKS upgrade

The other day I was monitoring an AKS Kubernetes version upgrade but the notifications Azure Portal had stopped updating. I found out that I can check the status from the command line.

emilyzall@Emilys-MBP ~ % az aks show -g my-rg -n my-cluster --query 'provisioningState'
"Upgrading"
emilyzall@Emilys-MBP ~ % az aks show -g my-rg -n my-cluster --query 'provisioningState'
"Succeeded"