diff --git a/aks/postgres/resources.tf b/aks/postgres/resources.tf
index 7129e02..ba73673 100644
--- a/aks/postgres/resources.tf
+++ b/aks/postgres/resources.tf
@@ -10,6 +10,17 @@ locals {
   azure_enable_monitoring     = var.use_azure && var.azure_enable_monitoring
 
   kubernetes_name = "${var.service_name}-${var.environment}-postgres${local.name_suffix}"
+
+  alert_frequency = local.alert_frequency_map[var.alert_window_size]
+
+  alert_frequency_map = {
+    PT1M  = "PT1M"
+    PT5M  = "PT5M"
+    PT15M = "PT15M"
+    PT30M = "PT30M"
+    PT1H  = "PT1H"
+  }
+
 }
 
 # Username & password
@@ -172,6 +183,7 @@ resource "azurerm_monitor_metric_alert" "memory" {
   scopes              = [azurerm_postgresql_flexible_server.main[0].id]
   description         = "Action will be triggered when memory use is greater than 75%"
   window_size         = var.alert_window_size
+  frequency           = local.alert_frequency
 
   criteria {
     metric_namespace = "Microsoft.DBforPostgreSQL/flexibleServers"
@@ -200,6 +212,7 @@ resource "azurerm_monitor_metric_alert" "cpu" {
   scopes              = [azurerm_postgresql_flexible_server.main[0].id]
   description         = "Action will be triggered when cpu use is greater than ${var.azure_cpu_threshold}%"
   window_size         = var.alert_window_size
+  frequency           = local.alert_frequency
 
   criteria {
     metric_namespace = "Microsoft.DBforPostgreSQL/flexibleServers"
@@ -228,6 +241,7 @@ resource "azurerm_monitor_metric_alert" "storage" {
   scopes              = [azurerm_postgresql_flexible_server.main[0].id]
   description         = "Action will be triggered when storage use is greater than ${var.azure_storage_threshold}%"
   window_size         = var.alert_window_size
+  frequency           = local.alert_frequency
 
   criteria {
     metric_namespace = "Microsoft.DBforPostgreSQL/flexibleServers"
diff --git a/aks/postgres/variables.tf b/aks/postgres/variables.tf
index 98beb73..40ce8db 100644
--- a/aks/postgres/variables.tf
+++ b/aks/postgres/variables.tf
@@ -124,13 +124,21 @@ variable "azure_enable_monitoring" {
   default  = true
 }
 
+
+
 variable "alert_window_size" {
-  type        = string
-  nullable    = false
-  default     = "PT5M"
+  type     = string
+  nullable = false
+  default  = "PT5M"
+  validation {
+    condition     = contains(["PT1M", "PT5M", "PT15M", "PT30M", "PT1H"], var.alert_window_size)
+    error_message = "The alert_window_size must be one of: PT1M, PT5M, PT15M, PT30M, PT1H."
+  }
   description = "The period of time that is used to monitor alert activity e.g PT1M, PT5M, PT15M, PT30M, PT1H, PT6H or PT12H"
 }
 
+
+
 variable "azure_maintenance_window" {
   type = object({
     day_of_week  = optional(number)