Edgar McGregor

On December 17, 2024, the Southern California Edison weather station that is bolted to a powerline next to the Pinecrest Gate at Eaton Canyon observed something rather remarkable. At 10:50 PM, the station recorded an air temperature of 74.4°F as a 14 MPH Santa Ana breeze swept past it. This beat the previous afternoon’s observed high of 73.7°F, meaning the weather station set its daytime high temperature a full five hours after sun set in the month of December!

This early-winter warm spell has been part of a larger problem facing Eaton Canyon and Southern California in general this year. It is December 25th, and yet another week has gone by without any meaningful rainfall. Eaton Creek is running dry, soils are parched, and vegetation remains dust-ridden. The fourth wettest month of the year, December, will end as a total shutout in 2024 with no measurable rainfall at the official Pasadena weather station. This has only happened four other times in 118 years of precipitation record-keeping.

Having just come off our wettest 18-month period on record between November 2022 and April 2024, and our driest 18-month period on record between April 2020 and November 2021, this extreme precipitation whiplash is hitting local ecosystems hard. The 2020s have been marked by either feast or famine, and that trend has only continued. As a result of this, MyEatonCanyon.com can unfortunately report that hundreds of young Western Sycamore and White Alder saplings that sprouted alongside the creek following the uber-wet winter 2023 rains have perished. Some had attained heights of up to 8′ before succumbing to drought.

As it stands, Pasadena is currently experiencing its driest June 1st – December 25th period ever recorded with just 0.07,” besting the 0.11″ record set in 2020. At Eaton Canyon itself, just 0.13″ has fallen at Eaton Dam while up to 0.59″ has fallen at Camp Hi-Hill behind Eaton Saddle. These numbers are even worse than those seen in 2020 and 2017, both of which were other exceedingly dry years.

Taking a look at creek flow, however, flow extent still remains prevalent following the drenching rains of winters 2023 and 2024. As of the December 1st survey, 47.9% of the creek is flowing between the waterfall and the New York Drive bridge. This isn’t all that much worse than 2023, and many young White Alder and Sycamore saplings that are growing where the creek is still flowing are alive and well.

The long term pattern continues to look highly unfavorable for precipitation as a huge ridge of high pressure sets up over the eastern Pacific just off the coast of California. January 2025 already looks like it will also be a bone dry month, with few if any storms managing to break through.

Concerns about a significantly below average or even record dry winter in Southern California are mounting as Pacific storms continue to fall apart before reaching the region. MyEatonCanyon.com will continue to monitor the growing drought situation with monthly creek-flow surveys continuing as normal. 

 

Throughout the months of November and December 2024, the Los Angeles County Department of Public Works has been and will continue to reconstruct Altadena Drive between New York Dr. and the Midwick Gate. This project is occurring in an effort to improve asphalt conditions which have deteriorated after decades of storms and traffic. During construction, the main Eaton Canyon gate will remain open to ingress access only. All vehicles are required to exit the park onto New York Dr. via the overflow parking lot. Any vehicle caught bypassing barriers and closed gates attempting to exit through the main gate may be cited by county sheriffs’ officers.

In July, MyEatonCanyon.com reported on a single-car traffic accident by the Midwick Parking Pad that was due to excessive speeding and commented on the dangers of Altadena Dr. to Eaton Canyon visitors. According to the project outline, which is provided here, there are no plans to create safe crosswalks for pedestrians exiting the Eaton Canyon Main Entrance at this time. Comments on the project to team managers may be emailed to [email protected]. 

 

Over the past 2 years, MyEatonCanyon.com has been monitoring changes to Eaton Canyon following the drenching winter 2023 rains, publishing articles on rain totals, tree sapling growth, and creek flow. Eaton Canyon has an exceedingly rare semi-arid Mediterranean climate type, in that not only do we have a winter wet season and summer dry season that is atypical throughout planet Earth, but our wet and dry seasons are far more pronounced than traditional Mediterranean climates. This fact puts Eaton Canyons’ ecology in an awkward position where it must be able to handle both several feet of rainfall in some years and 8+ month stretches without a single drop.

As we head into late autumn in Southern California, attention turns towards the equatorial East Pacific around and west of the Galapagos Islands. This particular part of the Pacific ocean undergoes periodic and regular sea surface temperature changes that impact the global weather in a phenomena we call the “El Nino Southern Oscillation” or “ENSO” for short. When ocean temperatures in this area are warmer than average, we call it El Nino. When they are cooler than average, we call this La Niña. These two episodes can last anywhere between 6 months and 3 years. La Niña conditions typically result in drier than average winters in California, though this is a generalization, not a rule. Famously wet years in the Golden State such as 2023 were La Niña years.

La Niña years more often than not generate persistent atmospheric ridging over or just west of California during the winter months, deflecting incoming Pacific rainstorms north into British Columbia. Meanwhile, El Nino years more often than not feature a strong subtropical jet stream that connects moisture between Hawai’i and the Southern California coast and can easily cut through those same ridges.

 

As of October 2024, the National Oceanic and Atmospheric Administration has a “La Niña Watch” in effect with cooler than average water temperatures in the equatorial east Pacific expected this winter. Earlier forecasts issued this past summer by NOAA called for more robust La Niña than we are currently seeing, and we’ve instead been hovering around neutral ENSO conditions. While conditions are still within the forecast envelope from last autumn, reality has been on the warm side.

 

Indeed, forecast models have begun calling for below average winter rainfall across the entire state, including Eaton Canyon. While these forecasts could very well be wrong, especially on a local level, optimism is not high for a wet winter 2025.