# Can forest fires cause rainstorms? **URL:** \ **Category:** Factual Questions\ **Created:** [April 24, 2011, 5:02pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566 "2011-04-24T17:02:51Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Novalyne](https://avatars.discourse-cdn.com/v4/letter/n/22d042/32.png) [@Novalyne](https://boards.straightdope.com/u/Novalyne)\ **Post date:** [April 24, 2011, 5:02pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/1 "2011-04-24T17:02:51Z")
I may be really misremembering this, but I could swear I watched a news piece or documentary some years back about forest fires, in which one of the reporters or scientists said that forest fires could be big enough to change weather patterns. I don’t remember the specifics, but it had something to do with the smoke going into the atmosphere, which eventually caused rain. So, a bit of a “natural” control for fires that began to rage out of control. Searches since then have been fruitless. Was I dreaming this? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [April 24, 2011, 5:50pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/2 "2011-04-24T17:50:14Z")
I’m no expert on weather, but it is my understanding that to some degree, this is true. It’s basically the whole idea behind cloud seeding. If you’ve got moisture in the air, adding particles for it to concentrate around and stick to will cause the water to condense and form rain. It only works if you have enough moisture in the air to start with though, and even then your rain may end up falling downwind of where your fire is, which is not going to be terribly useful for putting your fire out. Exactly how well and under what circumstances this works still seems to be a matter of some debate. In Indonesia, farmers and plantation owners regularly set fire to large areas in order to clear them of trees for farming. They intentionally time their burning to occur just before the monsoon season, and they claim that the smoke from the fires causes rain which will then put the fires out. It’s hard to say exactly how much of their rain is caused by smoke and how much of it would have occurred naturally. There was a study done in the Amazon a few years ago that came to the opposite conclusion, though. They found that there was indeed a difference in clouds in areas where there was a lot of smoke from forest fires. However, what they found was that the clouds from the smoky areas had more water droplets in them, but these droplets were smaller and tended not to precipitate. So the smoke particles, while causing water to condense, actually resulted in less rain and not more. ---
**Author:** ![sitchensis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sitchensis/32/4892_2.png) [@sitchensis](https://boards.straightdope.com/u/sitchensis)\ **Post date:** [April 24, 2011, 6:31pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/3 "2011-04-24T18:31:43Z")
The column of warm moist air that a wildfire creates has the potential to travel deep into the cold atmosphere. By cooling that warm air, the moisture condenses out and can form rain, and sometimes hail. This is the same principle that causes hurricanes, tornados and regular thunder storms. The only difference is the power source for the warm air lifting is a fire instead of the sun heating the earth. In my experience the rain is patchy and sporadic and never really even wets the ground. Its use as a “natural” fire control is pretty much non-existent. You have to realize that the same process that’s lifting the moisture is also lifting fire brands and tossing them ahead of the fire. A large wind driven fire rolls like a freight train, in many cases not even winter can put them out. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [April 24, 2011, 6:51pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/4 "2011-04-24T18:51:57Z")
the air movement and smoke can cause lightning which can start new fires in a dry fire prone situation. ---
**Author:** ![Harvey\_The\_Heavy](https://avatars.discourse-cdn.com/v4/letter/h/c5a1d2/32.png) [@Harvey\_The\_Heavy](https://boards.straightdope.com/u/Harvey_The_Heavy)\ **Post date:** [April 25, 2011, 9:33am UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/5 "2011-04-25T09:33:14Z")
Don’t know about forest fires, but in Kuwait during the first Gulf War, the burning oil rigs did indeed cause rain. Not enough to put the fires out though. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [April 25, 2011, 4:19pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/6 "2011-04-25T16:19:11Z")
Yes. A forest fire can be of sufficient size, combined with local weather, to produce rain downwind. It’s not uncommon for the smoke column on a large fire to approach 40,000 feet or more. The particulate matter combines with the high level moisture and effectively “seeds” the column to later produce precipitation. The same may apply to volcanic eruptions as well. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [April 25, 2011, 10:12pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/7 "2011-04-25T22:12:56Z")
I think it is more than just putting particulate matter up in the air. One of the byproducts of burning wood is water (one of the reasons water does not burn is because it is already burnt…in a manner of speaking). Not to mention trees have a lot of water as well which will get boiled off. You are now throwing a substantial amount of water (from a large forest fire) into the upper atmosphere. What goes up must come down. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [April 26, 2011, 10:04pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/8 "2011-04-26T22:04:59Z")
> [@sitchensis](#): > > The column of warm moist air that a wildfire creates has the potential to travel deep into the cold atmosphere. By cooling that warm air, the moisture condenses out and can form rain, and sometimes hail. > > This is the same principle that causes hurricanes, tornados and regular thunder storms. The only difference is the power source for the warm air lifting is a fire instead of the sun heating the earth. > > In my experience the rain is patchy and sporadic and never really even wets the ground. Its use as a “natural” fire control is pretty much non-existent. You have to realize that the same process that’s lifting the moisture is also lifting fire brands and tossing them ahead of the fire. A large wind driven fire rolls like a freight train, in many cases not even winter can put them out. Convection (which you describe) is the cause of rain. Hurricanes, tornadoes, and thunderstorms cannot be lumped into one category. Each has different causes and are multifactorial, but that is not relevant to the OP. ---
**Author:** ![sitchensis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sitchensis/32/4892_2.png) [@sitchensis](https://boards.straightdope.com/u/sitchensis)\ **Post date:** [April 27, 2011, 1:22am UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/9 "2011-04-27T01:22:03Z")
I realize it was simplified, but I stand by what I said. Atmospheric instability is the cause of all three. Warm moist air traveling upward is the power source that drives all three engines. ---
**Author:** ![user\_hostile](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/user_hostile/32/474_2.png) [@user\_hostile](https://boards.straightdope.com/u/user_hostile)\ **Post date:** [April 27, 2011, 2:19am UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/10 "2011-04-27T02:19:02Z")
Here’s my take on the power of convection: Flying the downwind leg of landing approach at a glider field (about 1200 AGL), a tractor doing some plowing caused a spark and generated a fire adjacent to the landing zone. The fire was about 50 yards long, burning fast with a little column of smoke, but it wasn’t enough to obstruct my field of vision. Rather than go around it, I flew through it. Even though I was straight and level, it felt like I’d done a 50° banked turn for about 1/2 second, and then weightless for the other 1/2 second. Made a mental note that had I cut 10 yards to the right or left of the column, the roll imparted to the respective left or right wing of the aircraft, the journey would be even more interesting. Never encountered a normal thermal with that kind of power (east coast). So yeah, I would argue that a forest fire could jump start a storm far more quickly than nature given the correct atmospheric conditions. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [April 27, 2011, 3:28am UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/11 "2011-04-27T03:28:25Z")
Here’s an interesting Wiki article on fire clouds or [Pyrocumulus](http://en.wikipedia.org/wiki/Pyrocumulus_cloud). > [@](#): > > A pyrocumulus cloud can help or hinder a fire. Sometimes, the moisture from the air condenses in the cloud and then falls as rain, often extinguishing the fire. There have been notable examples where a large firestorm has been extinguished by the pyrocumulus that it created. However, if the fire is large enough then the cloud continues to grow and becomes a type of cumulonimbus cloud. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [April 27, 2011, 4:41am UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/12 "2011-04-27T04:41:11Z")
> [@Whack-a-Mole](#): > > I think it is more than just putting particulate matter up in the air. > > One of the byproducts of burning wood is water (one of the reasons water does not burn is because it is already burnt…in a manner of speaking). Not to mention trees have a lot of water as well which will get boiled off. You are now throwing a substantial amount of water (from a large forest fire) into the upper atmosphere. > > What goes up must come down. An omission on my part. Thanks. But not always. I’ve been on fires where the fuel moisture content (MC) values approach 0.00 percent. I’m not just talking twigs that are bone dry and you can snap them in half just by looking at them. I’m talking 1,000 hour dead fuel moistures. These are logs up to six inches in diameter. Kiln dried lumber (2x4s and 2x10s) used to build your home is often between six and 18 percent MC. Some moisture content within building materials is not only desirable, but necessary to ensure lumber integrity. Of course, you might think dead standing, and dead and down measured for MC is a ringer. Actually the dead fuel MC creates a baseline for measuring not just within a specific fire, but forest stands across the country. Wildland fire takes live vegetation as well. Different species have different fire tolerance values. Many tree species actually require fire in order to propagate and thrive. And all this leads to those fire storms when all bets are off. Fires where live standing trees literally explode as the moisture (sap and water) vaporize. The moisture release can be so fast and at ground level that it dissipates before it can rise to a level where it could return later as precipitation. This is where the particulate matter seeds the existing moisture at much higher atmospheric levels as the single source for precipitation. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [April 27, 2011, 4:48am UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/13 "2011-04-27T04:48:28Z")
> [@Xema](#): > > Here’s an interesting Wiki article on fire clouds or [Pyrocumulus](http://en.wikipedia.org/wiki/Pyrocumulus_cloud). > > > [@](#): > > > > There have been notable examples where a large firestorm has been extinguished by the pyrocumulus that it created. Too bad the Wikipedia article did not offer any of those “notable examples.” Yes, fire clouds can generate precipitation that falls back on a fire. I’ve yet to see a fire cloud extinguish any fire that created it. However, my observed bias is that the larger fire weather doesn’t support enough self-generated precipitation. Perhaps wildland fire in the Tropics is where this occurs. ---
**Author:** ![psthomas01](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@psthomas01](https://boards.straightdope.com/u/psthomas01)\ **Post date:** [August 16, 2014, 2:09pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/14 "2014-08-16T14:09:34Z")
there has been plenty of wildfire smoke from recent fires, Sunday morning I could smell smoke in Lexington KY and then it rain a record amount. (as later did in Detroit, Long Island, etc) I am wondering if the wildfire smoke from out West and/or Canada served to seed the clouds from Gulf moisture, resulting in abnormally heavy rain. Do the particulates help moist gulf air condense into water droplets! ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [August 17, 2014, 11:58pm UTC](https://boards.straightdope.com/t/can-forest-fires-cause-rainstorms/579566/15 "2014-08-17T23:58:46Z")
Firestorm in itself is a weather condition, where the fire creates wind that draws more oxygen to feed the fire.