What is hydroclimate whiplash and how did it fuel the Los Angeles wildfires?

Los Angeles is burning.  The fires that began on January 7, 2025, continue to rage, with three wildfires having devastated large parts of Los Angeles city and its surrounding areas.

As of January 13, the blazes have claimed 25 lives and reduced 12,000 structures to ashes, covering an area of 155 square kilometres at the time of reporting. The fires have intensified further due to strong winds in the following days.

But how did all of this happen?

Firstly, forest fires are a natural part of the life cycle of forests. However, in California, they have become more severe due to human-induced climate change, along with other factors such as urban encroachment. Additionally, recent reports suggest that the ongoing series of fires may have been exacerbated by a rare meteorological phenomenon, enhanced by climate change, known as ‘hydroclimate whiplash’.

So, what exactly is hydroclimate whiplash and how did it contribute to the escalation of the fires in Los Angeles?

Hydroclimate whiplash refers to rapid swings between intensely wet and dangerously dry weather, a phenomenon that is increasing worldwide. This repeated shift between prolonged extremes is an unusual and concerning trend.

Let’s break this down in the context of California.

The early part of the 2024 Californian season was predominantly wet, which encouraged the growth of vegetation. However, this was followed by a prolonged period of dry, drought-like conditions. As of January 7, 2025, almost 36 per cent of California was experiencing moderate to extreme drought, while 100 per cent of Los Angeles County was under severe to moderate drought conditions. The wet season, which typically begins in October and helps with the natural regeneration of forests, did not occur during the 2024-25 period. During this time, the overgrown vegetation dried out, becoming a fire hazard.

Moreover, dry conditions in California often coincide with the Santa Ana winds season, creating ideal conditions for intense wildfires.

The Santa Ana winds, which play a crucial role in the spread of the Palisades, Eaton and Kenneth wildfires, occur when air from a high-pressure region over the dry, desert areas of the southwestern US flows westward towards low-pressure areas off the California coast.

As these dry winds descend the mountain slopes, they become compressed and warm. When combined with other factors, such as low levels of precipitation and humidity and higher long-term air temperatures, these winds significantly increase the risk of intense wildfires, as we have seen in California in recent days.

Global weather records show that hydroclimate whiplash has increased by 31 per cent to 66 per cent worldwide since the mid-20th century and climate change is accelerating this trend. With a further 3°C rise in global temperatures, the incidence of hydroclimate whiplash could increase by 113 per cent during sub-seasonal periods and by 52 per cent during inter-annual periods.

As the Palisades and Eaton fires, which originated in the Santa Monica and San Gabriel mountains respectively, continue to rage in the western and northern parts of Los Angeles, experts predict an increase in both the wettest and driest years in California for the foreseeable future.