Multiple services – Power/cooling issues in West US 2

Update timeline

1. monitoring May 29, 2026, 04:27 AM UTC

   Impact Statement: Starting at 04:27 UTC on 29 May 2026, we are investigating an incident which is impacting multiple services in West US 2, due to a power event. This impacts service accessibility in the region, with customers potentially experiencing increased latency and intermittent connectivity, including timeouts when connecting to resources. Current Status: We identified this issue through our automated monitoring after detecting elevated alerts related to network and infrastructure health in the West US 2 region. The issue was triggered by a power event in the datacenter, which impacted underlying infrastructure and led to increased latency and intermittent connectivity for select resources. We are aware of the impact and are actively investigating. Mitigation efforts are underway to restore affected network components across dependent services, including Storage and Compute. Customers may begin to see signs of recovery as these actions progress. The next update will be provided within 60 minutes, or sooner if there are significant developments.

2. monitoring May 29, 2026, 04:27 AM UTC

   Impact Statement: Starting at 04:27 UTC on 29 May 2026, a severe thunderstorm caused widespread utility power loss to our West US 2 datacenter facilities, resulting in a multi-service outage. Impact is currently region-wide, and we have not yet confirmed isolation to specific scale units or availability zones and are treating this as full-region impact until physical inspections confirm otherwise. Customers are experiencing service connectivity failures, timeouts, and elevated error rates across affected services. This includes an inability to deploy new resources or scale existing workloads, intermittent availability where some requests may succeed while others fail depending on which infrastructure nodes have recovered, and both data plane and control plane impact for services not yet restored. Affected Azure services include, but are not limited to:Azure Functions, Azure Database for MySQL Flexible Servers, Azure Database for PostgreSQL Flexible Server, Azure Databricks, Redis, Azure SQL, Azure Managed Grafana, Virtual Machines, Virtual Machine Scale Sets, Azure Kubernetes Service, Storage, Application Insights, Azure Data Factory, Azure Monitor, and Azure Log Analytics Current Status: Severe thunderstorms resulted to a complete utility power loss to multiple datacenter buildings simultaneously. Our backup generators activated but were unable to fully compensate. The generator transfer switchover was only partially successful, with some generator sets failing to synchronize under the sudden full facility load and others experiencing thermal protection shutdowns as ambient temperatures rose due to simultaneous cooling system failures. This cascading combination of power instability and cooling loss exceeded our designed N+1 redundancy for this failure mode. We are still determining the full extent of mechanical vs. electrical failures in the generator systems. HVAC systems are being restarted in sequence; ambient temperatures are returning to safe ranges but have not fully normalized, so we are staged-powering equipment to avoid thermal re-trips. Network devices and storage arrays are being power-cycled and validated in sequence, with storage dependencies as the primary remaining bottleneck due to required manual intervention and data integrity verification. Where possible, traffic is being redirected to healthy nodes, and on-site teams are conducting physical hardware inspections to identify components requiring replacement. The following services have been confirmed restored and are operating normally:Service Bus, App Service (Web Apps), Azure Site Recovery, Backup (MAB), Azure Cosmos DB, Azure Resource Manager, Data Explorer, Azure IoT Hub, Microsoft Defender for Cloud Apps, Azure Container Registry, Azure Policy, Azure NetApp Files, Azure Resource Graph, Azure Synapse Customer Guidance: • If you have resources in paired or alternate regions, consider failing over traffic away from West US 2 until we confirm full recovery. • Single-region workloads will recover automatically as infrastructure is restored — no customer action is required. • We recommend pausing new deployments to West US 2 until this incident is resolved; use alternate regions if urgent. • Monitor Azure Status (status.azure.com) and Service Health in the portal for real-time updates specific to your subscriptions. Next update: We will provide our next status update within 1 hour, or sooner, if events warrant.

3. monitoring May 29, 2026, 04:27 AM UTC

   Impact statement: Starting at 04:27 UTC on 29 May 2026, a severe thunderstorm caused widespread utility power loss across multiple West US 2 datacenter facilities, resulting in impact to multiple Azure services. Datacenter power has been fully restored, and the majority of network and storage infrastructure has recovered. Infrastructure in Availability Zone 2 has recovered and is operating normally. Residual impact is now concentrated on a subset of infrastructure within Availability Zones 1 and 3, where two storage stamps are undergoing final recovery and validation. Customers with resources deployed exclusively in Availability Zone 2 should not be affected by the remaining recovery activities; however, those with dependencies in Availability Zones 1 or 3 may continue to experience intermittent connectivity, elevated latency, or resource unavailability. Currently affected Azure services include, but may not be limited to (recovery validation underway):Azure Functions, Azure Database for MySQL Flexible Server, Azure Database for PostgreSQL Flexible Server, Azure SQL, Azure Managed Grafana, Virtual Machines, Virtual Machine Scale Sets, Azure Kubernetes Service, Azure Storage, Application Insights, Azure Monitor, and Azure Log Analytics.The following services have recovered and are operating normally:Service Bus, App Service (Web Apps), Azure Site Recovery, Backup (MAB), Azure Cosmos DB, Azure Resource Manager, Azure Data Explorer, Azure IoT Hub, Microsoft Defender for Cloud Apps, Azure Container Registry, Azure Policy, Azure NetApp Files, Azure Resource Graph, Azure Data Factory, Azure Databricks, Azure Cache for Redis, and Azure Synapse Analytics. Current Status: A severe weather event, including multiple lightning strikes, affected several datacenter facilities in the West US 2 region, resulting in concurrent utility power interruptions across multiple availability zones. Backup generators activated as designed; however, during the transition to sustained generator operation, a subset of generator systems were unable to fully synchronize under the sudden facility load, while others subsequently shut down due to thermal protection mechanisms as cooling systems were impacted by the broader power disruption. Because these events occurred across multiple facilities within the same timeframe, the resulting conditions exceeded the resiliency designed for this particular failure scenario. Datacenter utility power has been fully restored. HVAC systems have normalized, ambient temperatures have returned to expected operating ranges, and the majority of network and storage infrastructure has recovered successfully. While most services have returned to normal operation, a small subset of storage clusters and network devices did not recover cleanly and continue to limit full-service restoration. Some storage clusters remain partially unavailable or dependent on ongoing network recovery activities, and a limited number of network devices connecting compute resources to storage infrastructure remain impaired. As a result, some virtual machines are currently unable to access their underlying storage dependencies and may remain unavailable. Recovery efforts have transitioned from broad infrastructure restoration to targeted remediation of specific network devices, storage clusters, and isolated compute nodes. As these components are restored, validated, and returned to service, dependent workloads are recovering incrementally. Two storage stamps are currently completing final recovery and integrity validation activities, and services dependent on those stamps are expected to recover as this work is completed. Estimated Time to Resolution: With datacenter power restored and the majority of network and storage infrastructure recovered, remaining work is focused on two storage stamps completing final recovery and data integrity validation activities. Based on current progress, we estimate full-service restoration within approximately 2-3 hours. Individual services dependent on these stamps will recover progressively as validation activities are completed. Customer Guidance:Single-region workloads will recover automatically as infrastructure restoration activities are completed; no customer action is required.We recommend postponing new deployments into West US 2 until this incident is resolved and using alternate regions for urgent deployment needs.Logical availability zones assigned to customer subscriptions may map to different physical availability zones. Customers can use the Locations API to understand this mapping: https://learn.microsoft.com/rest/api/resources/subscriptions/list-locations?HTTP#availabilityzonemappings. Next Update: We will provide our next status update within 60 minutes, or sooner if significant progress is made.

4. postmortem May 30, 2026, 02:30 AM UTC

   Watch our 'Azure Incident Retrospective' video about this incident: https://aka.ms/air/GHRP-84G What happened? Between 04:24 UTC on 29 May and 02:30 UTC on 30 May 2026, customers with resources in the West US 2 region may have experienced failures when attempting to access or manage some Azure services in the region. Impact included connectivity failures, resource unavailability, and service management failures. The issue was triggered by a severe thunderstorm that caused utility power disturbances affecting multiple datacenter facilities serving the region. These disturbances led to some cooling systems entering a protective mode to preserve equipment integrity. This caused elevated temperatures which triggered proactive shutdowns of infrastructure affecting compute, networking, and storage systems across two different availability zones in the region (physical AZ-01 and AZ-03). After cooling systems stabilized, storage services - and the networking on which they depend - required extensive manual recovery actions, which contributed to the total duration of customer impact. The following services were among those affected: Application Insights, Azure App Service, Azure Backup, Azure Cache for Redis, Azure Container Registry, Azure Cosmos DB, Azure Databricks, Azure Data Explorer, Azure Data Factory, Azure Functions, Azure IoT Hub, Azure Kubernetes Service, Azure Monitor, Azure NetApp Files, Azure Resource Manager, Azure Site Recovery, Azure SQL Database, Azure Storage, Azure Synapse Analytics, Azure Virtual Machines, Log Analytics, Service Bus, and Virtual Machine Scale Sets. What went wrong and why? A severe thunderstorm produced lightning strikes, resulting in utility power disturbances across multiple datacenter facilities serving the West US 2 region. These disturbances affected a wide enough geographic area that a subset of datacenters within two Availability Zones experienced impact. While this event was not a complete utility power interruption, these datacenters experienced multiple voltage sag/swell events, meaning utility power remained present but was unstable. The region consists of datacenters built at different times with varying infrastructure designs, including differences in cooling control systems and power protection mechanisms. Some datacenters transferred to generator power, while others did not transfer, as the utility power source remained available even as voltage fluctuated. Independently of whether each datacenter transferred to backup power, a subset of components within the mechanical cooling systems - across multiple datacenters - detected abnormal electrical conditions and, by design, entered a 'lockout' protective state. This reduced cooling capability and prevented parts of the cooling system from automatically returning to normal operation after the power disturbance. As temperatures rose beyond safe operating thresholds, a subset of cloud infrastructure automatically shut down to prevent physical damage and preserve data integrity. Impacted cooling systems required manual intervention and troubleshooting, including multiple restart attempts before stable cooling capacity could be reestablished. Additionally, we had to identify which devices required manual recovery and which were expected to self-recover. Impacted Storage scale units required additional validation. These factors contributed to the extended recovery time for services dependent on storage, including telemetry processing systems. How did we respond? Recovery efforts began immediately, prioritizing cooling restoration, then network infrastructure, followed by compute and storage systems. Cooling was restored within approximately two hours of impact start. The majority of compute resources recovered within eight hours. Storage validation, which must be performed sequentially, extended over approximately 14 hours. Finally, telemetry services (Application Insights and Log Analytics) required an additional six hours beyond storage recovery to process accumulated backlogs. The timeline below details the progression of recovery: • 04:14 UTC on 29 May 2026 – Utility power sag/swells were observed across multiple datacenters. These caused a subset of the mechanical cooling systems to enter a 'lockout' protective state. • 04:24 UTC on 29 May 2026 – Customer impact began; our monitoring produced thermal alerts as temperatures rose due to reduced cooling functionality. • 04:31 UTC on 29 May 2026 – Manual cooling diagnosis and restoration efforts began. • 04:40 UTC on 29 May 2026 – As temperatures rose, some cloud infrastructure shut down to prevent damage. • 04:50 UTC on 29 May 2026 – Networking and Storage engineers began assessing infrastructure health and necessary restoration efforts. • 05:55 UTC on 29 May 2026 – All cooling was restored in impacted datacenters, and temperatures had stabilized. Assessments continued on remaining infrastructure issues. • 06:15 UTC on 29 May 2026 – Approximately 50% of impacted underlying Virtual Machines (VMs) had recovered. • 12:00 UTC on 29 May 2026 – Approximately 95% of impacted underlying Virtual Machines (VMs) had recovered, after premium Storage had been largely recovered. Compute and Storage teams continued to identify and mitigate remaining unhealthy nodes. • 18:46 UTC on 29 May 2026 – Storage was confirmed as the remaining recovery bottleneck; validation of Storage-specific issues was ongoing. • 20:18 UTC on 29 May 2026 – All affected services confirmed as recovered, except for Application Insights and Log Analytics which were still processing backlogs. • 02:30 UTC on 30 May 2026 – Customer impact for Log Analytics and Application Insights confirmed as mitigated. How are we making incidents like this less likely or less impactful? • First and foremost, we are reviewing and enhancing our operational processes for cooling system recovery based on learnings from this incident, to ensure that all employees have clear and documented actions to support faster recovery during high-stress scenarios. (Estimated completion: June 2026) • Our Log Analytics team is improving the resiliency of service startup processes so that transient initialization failures self-recover automatically, reducing the need for manual intervention during large-scale restarts. (Estimated completion: June 2026) • Our Networking team is addressing platform limitations that constrained the speed at which storage nodes could be returned to service following the thermal event. This includes reducing dependencies on manual coordination steps, and enabling faster parallel recovery of storage infrastructure. (Estimated completion: July 2026) • Our Networking team is also improving the tooling and processes used to identify which infrastructure devices have entered protective states and require manual recovery. This includes developing clearer prioritization of foundational devices (such as management and networking components) earlier in the recovery sequence, and improving awareness across teams when thermal events affect shared infrastructure. (Estimated completion: August 2026) • Our Log Analytics team is improving the architectural resiliency of our telemetry processing services by enabling multi-cluster flexibility and support for a broader pool of compute resource types, reducing dependence on any single cluster or resource type's availability and improving the ability to recover during large-scale scenarios. (Estimated completion: August 2026) • Finally, in the longer term we are performing a joint, holistic engineering review to evaluate the fail-state behavior of the cooling system protection logic. The current system prioritizes equipment protection and data security over operational continuity, which resulted in a full lockout rather than staged or degraded operation. This includes evaluating proactive row-level shutdown strategies during rapid temperature increases, and expanding the decision-making window available to operators before protective systems engage. (Estimated completion: October 2026) How can customers make incidents like this less impactful? • Note that the 'logical' Availability Zones used by each customer subscription may correspond to different physical Availability Zones - customers can use the Locations API to understand this mapping, to confirm which resources run in which physical AZ: https://learn.microsoft.com/rest/api/resources/subscriptions/list-locations • For mission-critical workloads, customers should consider a multi-region geodiversity strategy to avoid impact from incidents like this one that impacted a single region: https://learn.microsoft.com/en-us/azure/architecture/patterns/geodes and https://learn.microsoft.com/en-us/azure/well-architected/design-guides/regions-availability-zones • Consider leveraging data redundancy options such as Geo-Redundant Storage (GRS) or Read-Access Geo-Redundant Storage (RA-GRS), which replicate data to a secondary region and can provide continued read access to data during regional incidents: https://learn.microsoft.com/azure/storage/common/storage-redundancy • More generally, consider evaluating the reliability of your applications using guidance from the Azure Well-Architected Framework and its interactive Well-Architected Review: https://aka.ms/AzPIR/WAF • The impact times above represent the full incident duration, so are not specific to any individual customer. Actual impact to service availability varied between customers and resources. For guidance on implementing monitoring to understand granular impact: https://aka.ms/AzPIR/Monitoring • Finally, consider ensuring that the right people in your organization will be notified about any future service issues by configuring Azure Service Health alerts. These can trigger emails, SMS, push notifications, webhooks, and more: https://aka.ms/AzPIR/Alerts How can we make our incident communications more useful? You can rate this PIR and provide any feedback using our quick 3-question survey: https://aka.ms/AzPIR/GHRP-84G