The US wildfire season of 2021 is already off to a bad start—and it looks like things are only about to get worse.
According to the National Interagency Fire Center, there’s substantial fire activity in at least 12 states across the US and at least 99 active large fire complexes. In total, at least 2.5 million acres (1 million ha) have burned and more than 26,500 wildland firefighters and support personnel have been dispatched to fires around the country.
Of course, the bulk of the fires are occurring in frequently dry areas, such as California, northern Idaho, and western Montana, though we’re also seeing some sizable complexes form in Washington state—even in the typically wet North Cascades.
Overall Climatic Setting
Wildfires are a natural occurrence throughout much of North America and fire regimes are a necessary part of the health of many ecosystems, particularly. in the western part of the continent. However, we’re seeing an increased amount of fire activity in recent years, likely due to the effects of anthropogenic climate change.
Globally, July 2021 was the hottest month in recorded history, and the temperature anomalies that we’ve seen in the US recently certainly support that statement.
The above image from NOAA clearly shows a strong positive temperature anomaly over the western US where most of the fire activity is occurring. The below image from ClimateReanalyzer.org also shows a sizable positive temperature anomaly over much of the US (and elsewhere) for August 21, 2021.
However, warming temperatures are only one part of the story. July 2021 was also a particularly dry month in the western part of North America, as seen below in a precipitation anomaly chart from NOAA.
Parts of the western US and western Canada have seen negative precipitation anomalies of upwards of 40 mm in the past month. This lack of precipitation sets the stage for very dry conditions. When combined with the hot temperatures we’ve seen recently, these dry conditions are the perfect opportunity for fire ignition throughout the west, whether the fire is natural or human-caused.
Current Fire Weather Outlook
At this point, it’s clear that hot, dry conditions have settled in throughout western North America. But, hot, dry conditions on their own don’t necessarily mean that fires will range.
The Storm Prediction Center (SPC) is currently issuing an elevated risk of fire weather throughout the northern part of the Great Basin. Much of this increased risk is due to the approach of a mid-level short-wave trough that’s making its way southward from the Pacific Northwest.
According to the SPC, this approaching trough will encourage divergence aloft, further mixing the boundary layer and setting the stage for isolated dry thunderstorms.
At the same time, there’s a cold front rapidly making its way toward the region. This cold front will bring with it dry and breezy conditions, particularly after it passes. We’ll see only increased fire risk after the cold front, particularly as breezy conditions tend to fuel fire growth.
Either way, if you’re located in a high fire-risk locale, always remember to heed local advice and respect all evacuation orders. Fires spread quickly and they’re nothing to mess with.