Fire Suppression

The multi-day spate of widespread lightning activity in the second half of June produced a 9-day total of about 57,000 cloud-to-ground lightning strikes, according to the Alaska Fire Service's detection network.  It was a substantial wave of activity, but not all that unusual in the context of historical data since 2012; four other years had larger 9-day totals (2025, 2015, 2019, 2022), with the record being last year's 69,000 strikes that occurred just a few days earlier on the calendar.

As noted previously, the lightning outbreak was unusual for the level of activity in the southwest and northern interior regions.  The Lower Yukon zone, in particular, saw a very intense onslaught compared to the climatological normal, and the year-to-date activity there is already tied with the 2019 record for the entire season.

Here's the actual strike density in absolute terms for the month of June:

The northwestern and southeastern interior were relatively inactive, with the most notable shortfall being in the Koyukuk and Upper Kobuk zone:

It has been something of a surprise to see wildfire activity remain very subdued despite all the lightning.  There have been fire starts, of course, but they haven't grown; statewide acreage is only 29,000 acres, a mere 10% of the climatological median.  The chart below shows that the disparity between the number of fire starts and fire acreage is very unusual; no other year since 1993 had so little acreage with more than 100 new fires in June.

Similarly, the fire acreage relative to the number of lightning strikes is extremely low:

Although last year had more fire, it was qualitatively similar: somewhat subdued fire growth relative to the extensive lightning activity.  At least one key factor is that both years had a wet spring across most of the fire-prone interior:

Contrast this with 2022, for example, which saw very efficient fire growth (a lot of acres per fire and per lightning strike) after a dry (but not warm) spring:

Of course the weather in June also makes a huge difference for the fate of lightning-sparked fires; 2004 and 2013 were extremely warm in June, and fire growth was rapid.  Last month had some warm days, but the second half of the month was near-normal for Fairbanks temperature overall; and there's been a substantial amount of rain in many areas in the past two weeks.  Obviously when lightning is accompanied by widespread and significant rain - as opposed to "dry" thunderstorms - the fire activity is more often suppressed.

Not surprisingly, there is a correlation between June fire acreage and the rest of the season (fires tend to keep burning), but the weather is the key factor.  For instance, 2009 was extremely warm and dry in July, producing big fire activity after a slow start.  Hopefully we won't see anything similar this year.