California Current Marine Heatwave Tracker

An experimental tool for tracking marine heatwaves

Latest Conditions

Daily sea surface temperature anomalies (SSTa) in the California Current ecosystem. SST data from Multi-scale Ultra-high Resolution (MUR) SST Analysis Anomaly

Current conditions update 7-10-26

We are currently tracking two large marine heatwaves in the Northeast Pacific region (Fig. 1, Fig. 2). The first one, denoted NEP25A, is located near the coast of central and southern California, whereas the second one, denoted NEP26A, is to the far west of the region between 37-47°N latitude. NEP25A has been a contiguous feature that we have tracked since May of 2025 (hence its name, NEP25A, which denotes it as the first large MHW tracked starting in 2025); NEP26A developed in May 2026 in the far offshore region. Along the northern California coast through Washington, coastal temperatures are cooler than normal, indicating strong coastal upwelling, which is typical for that region for this time of year.

NEP25A reached its maximum size during September 2025 (Fig. 3b, Fig. 4) and then decreased greatly in area during October and November 2025 (Fig. 4b), following an annually consistent pattern for most MHWs in recent years. Unlike previous years, however, NEP25A then expanded again during December 2025 along the southern California coast, where it has continued to persist in the nearshore waters. Current coastal sea surface temperatures (SST) off southern California are among the warmest ever seen for this time of year, rivaled only by the “Warm Blob” years of 2014-2015. It is important to note that these current temperature anomalies off California are not yet due to El Niño, which will most likely start to affect water temperatures in this region during fall 2026 and into winter 26/27. 2026A, the second MHW we are tracking in the region, has slowly expanded in size over the past month and continues to follow the typical pattern of the far offshore events, which tend to slowly enlarge over the summer and often may impact the coast during the later summer or into the fall.

The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests a high likelihood that marine heatwaves will continue through the summer and fall in the offshore regions, with increasing likelihood of marine heatwaves in coastal regions (particularly off California). The El Niño forecast (as of June) reports that we are now in an “El Niño advisory” status, with a high probability of El Niño strengthening to “very strong” category during the fall and winter (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml).

Although the current MHW off California may appear to be “preconditioning” the region with above-average water temperatures before we encounter additional warming this fall due to El Niño, the two features may not necessarily be additive. Rather, we suspect that greater impacts may accrue from the prolonged duration of warmer than normal temperatures in the coastal region. Essentially the coastal zone may transition from anomalously warm waters associated with the current marine heatwave right into similarly warm waters due to the El Niño, somewhat matching the observations in 2015 when we also transitioned from “The Blob” to another moderately strong El Nino during winter 2015-16. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.

Animations and images of past years’ developing heatwaves can be found here: NEP25A animation, NEP24A animation, NEP23A animation; previous archived animations.

View new and ongoing analyses highlighting regional conditions associated with individual West Coast National Marine Sanctuaries and states (Washington, Oregon, and northern, central, and southern California).