Increased Error Rate and Latency in US-EAST-1 (use1-az4 thermal event)
AWS Health Dashboard timeline for the thermal event that impaired a single Availability Zone (use1-az4) in the US-EAST-1 Region, beginning May 7, 2026.
May 8, 2026 00:53 UTC — We continue to investigate instance impairments to a single Availability Zone (use1-az4) in the US-EAST-1 Region. We have experienced an increase in temperatures within a single data center, which in some cases has caused impairments for instances in the Availability Zone. EC2 instances and EBS volumes hosted on impacted hardware are affected by the loss of power during the thermal event. Other AWS services that depend on the affected EC2 instances and EBS volumes in this Availability Zone, may also experience impairments.
May 8, 2026 10:54 UTC — At this time, we wanted to provide some more details on the issue. Beginning on May 7 at 4:20 PM PDT, we began experiencing an increase in instance impairments within the affected zone due to the loss of power during a thermal event. Engineers were automatically engaged within minutes and immediately began investigating multiple mitigations. By 9:12 PM PDT, we restored power to a subset of the affected infrastructure and observed some signs of recovery, which have remained stable. We continue working to bring additional cooling system capacity online, which will enable us to recover the remaining affected hardware in the impacted zone in a controlled and safe manner. If immediate recovery is required, we recommend customers restore from EBS snapshots and/or replace affected resources by launching new replacement resources in one of the unaffected zones.
May 8, 2026 13:51 UTC — We continue working to resolve the impaired EC2 instances and degraded EBS volumes in a single Availability Zone (use1-az4) in the US-EAST-1 Region caused by a thermal event. During such an event, servers automatically shut down when the temperatures exceeded the operating thresholds in order to protect the hardware. In parallel, we are investigating increased error rates and query failures for Redshift clusters in the US-EAST-1 Region.
May 8, 2026 15:58 UTC — As part of our parallel investigation, we have identified the root cause of the increased error rates and query failures for Redshift clusters in the US-EAST-1 Region. This has been confirmed to be related to impact from an upstream dependency. Our timeline for full recovery is still expected to take several hours and will be incremental as we bring racks online in phases.
May 9, 2026 03:04 UTC — Starting May 7 4:20 PM PDT, we experienced increased impaired EC2 instances and degraded EBS volumes in a single facility (data center) within a single Availability Zone (use1-az4) in the US-EAST-1 Region. The issue was caused by a thermal event resulting in a loss of power. As part of our recovery effort, we shifted traffic away from the impacted Availability Zone for most services at May 7 5:06 PM. AWS services, like Elastic Load Balancing, Elastic Kubernetes Service, ElastiCache, Redshift, OpenSearch, Managed Streaming for Apache Kafka among others, that depend on the affected EC2 instances and EBS volumes in this Availability Zone, also experienced elevated error rates and latencies for some workflows and/or configurations. Our main effort during the event mitigation strategy was to bring back our cooling systems capacity. By May 8 1:50 PM, we were able to stabilize cooling system capacity to pre-event levels, which helped us to restore the majority of the impaired EC2 instances and EBS volumes. A small number of instances and EBS volumes remain impaired and we continue to work to recover all affected remaining resources.