Did you know that spring weather significantly influences a region’s wildfire activity during the summer? The main reason for this is that spring weather (wet vs dry) helps dictate how much new vegetation grows in the way of grasses and shrubs. Additionally, the spring weather affects how moist the existing dead wood will be during the summer.

The amount of new vegetation growth and the amount of existing dead vegetation during the spring affect what is called the ‘fuel load’ for wildfires in the summer. Another factor is drought, which can affect both the amount of fuel available as well as the moisture characteristics of that fuel. 

With wildfire season expected to become more active over the next couple of months and already starting in Canada, let’s take a deeper look into the science of spring weather and fuel loads, as well as where the fuels are currently most likely to ignite wildfires. 

Satellite smoke map (top) and active wildfire map (bottom). 

What is the ‘Fuel Load’ and How Does it Affect Wildfires?

The fuel load is defined as the total amount of combustible material in a defined space. Fuel load is quantified in heat units or in its equivalent weight in wood. A given area with more wood, grass, or shrubs that are drier will have a greater fuel load. The fuel load increases as temperatures warm, humidity decreases, and with less precipitation. 

The fuel load is an important variable that meteorologists and wildfire operations monitor because it helps determine when wildfires can occur and spread into large fires. If a given area experiences a wildfire but the vegetation is still moist, the wildfire will not spread as rapidly, given the same conditions, but with dry vegetation.

Wildfires are most likely to ‘blow up’ when fuels are plentiful and unusually dry from drought. The availability for wildfires to grow and spread depends on many other factors in the environment and atmosphere, such as the micro-climate, soil conditions, atmospheric stability, terrain steepness, and more. We’ll cover these topics in News Articles throughout the summer and fall.

How Spring Weather Affects the Fuel Load

The weather in the spring is a major contributor to the fuel load. A wet spring will mean that more vegetation can grow and thus increase the fuel load (as long as it dries out eventually). A wet spring will also mean that existing dead wood will stay moist longer.

A dry spring, on the other hand, can lead to a faster start of wildfire season but may cause less fuel loads if there is not as much new vegetation growth. Past years' fuel loads can combine year after year, and may be a major contributor to a wildfire season as well.

In 2023, for example, a wet spring and early summer for many areas across the Western US (2023) was due in part to the record-setting snow pack for some areas. The above-average snowfall in 2023 caused above-average snow melt, and therefore more water availability, leading to more new vegetation growth.

Below is California, contrasting May 2022 on the left and May 2023 on the right. The additional snow present in May 2023 can potentially cause more significant wildfire conditions once the ‘green-up’ has dried out in the summer.

This means that due to a wet winter and or wet spring (for example in 2023 California), the potential for significant wildfire activity could increase by late in the season (late summer/early fall) if and when vegetation and fuels dry out. Wildfire seasons are not always worse with wetter winters and/or springs, but they can be a significant factor.

Connecting this to Wildfires

Wildfires need fuel, combustion, and favorable hot, dry, and windy weather to be the greatest hazard.

Once the fuel loads have accumulated due to spring and early summer vegetation growth, summer heat, and dry weather can cause fuels to become ready for combustion. The vegetation loses its moisture and becomes dry enough to allow wildfires to start and grow quickly. The summer is when the accumulation of the past few months of weather affects when, where, and how large wildfires can be. 

The National Weather Service issues Red Flag Warnings, which means critical fire weather conditions are occurring or will occur shortly. Critical fire weather conditions mean gusty winds with low relative humidity, which allow fires to spread and grow quickly.

Below is a look at the NWS Warnings and Advisories map from July 2024.

Where are the Fuels ready to Ignite?

The wildfire season is slowly beginning in the Western US with temperatures warming and fuels drying. While few to no wildfires have ignited thus far as of early June 2025 in the West, the wildfire season is expected to be above normal.

Many areas in the West saw a drier-than-normal spring, which is causing drought conditions. The dry spring and current drought conditions are on top of a dry winter (especially the Southwest), which will lead to dry fuels and favorable chances of an above-normal wildfire season.

Check out the current drought monitor as of June 3, 2025, across the Western U.S.

Hot, dry, and windy conditions will continue through June and are expected to increase drought conditions and lead to an above-normal wildfire season due to the combustion of dry fuel loads. Areas in drought are more prone to having dry fuels, which means wildfires are more likely.

Below is the National Interagency Fire Center’s Significant Wildland Fire Potential map for the months of June and July 2025. The above normal risk in red correlates with many areas currently in a drought. 

Many areas in the Pacific Northwest will see the highest chances of an above-normal wildfire season due to dry conditions this spring, which have caused favorable fuel loads for combustion.

An above-normal wildfire season is expected due to the drought conditions, along with the summer forecast of warm temperatures and dry conditions. Check out the Climate Prediction Center's (CPC) outlook of temperature (top) and precipitation (bottom) for June, July, and August 2025.

To see how wildfire smoke could disrupt your summer adventures, use the OpenSnow smoke map, which shows the location of forecasted wildfire smoke across North America and up to 60 hours (2.5 days) into the future. 

Zach Butler