<p>It's a combination of both the density and amount of smoke in the air and <a href="https://www.theguardian.com/australia-news/2020/jan/04/australia-bushfires-week-of-anger-scott-morrison" rel="noreferrer">ash</a> produced by the fire.</p>

<p>The thing about <a href="https://mobile.abc.net.au/news/2019-11-11/fire-weather-and-why-tuesday-looks-so-bad/11693894?pfmredir=sm" rel="noreferrer">cold fronts and bush fires</a> is they make the conditions for fire worse by pushing hot air in front of them. They have been blamed for the severity of the bush fires in Victoria in 2009, 1983 and 1939.</p>

CC BY-SA 4.0
2020-01-07T11:17:17.477Z
2020-01-07T11:27:51.570Z
2020-01-07T11:27:51.570Z
Fred
<p>It was a combination of thick smoke and pyrocumulus clouds. Possibly there might have been other types of cloud as well, Ash rising on the updraught may also have been a factor. I am informed that normal types of cloud sometimes made an appearance during the drought. Near-pitch darkness in daylight hours is also characteristic of volcanic eruptions, but I am not suggesting that volcanic eruptions were a factor in this case, though they make an analogy. </p>

<p>During cumulonimbus events in England, usually accompanied by rain and thunder, we often get very dim light in mid afternoon, long before evening time, though I wouldn't describe it as pitch darkness but more a sort of twilight. If enormous plumes of smoke were added, it very likely would have become almost pitch dark.</p>

CC BY-SA 4.0
2020-01-07T11:34:17.190Z
Not England? Well blow me down, I thought it was one of the southern counties!
Michael Walsby
CC BY-SA 4.0
2020-01-08T10:07:15.483Z
UK: I remember when the smoke from the Buncefield oil depot explosion/fire drifted overhead, thousands of feet up. It still looked sunny, but it was far too dark.
nigel222
CC BY-SA 4.0
2020-01-07T11:17:34.233Z
2020-01-07T11:17:34.233Z
Michael Walsby
<p>If you think how white smoke looks when it is rising elsewhere and you are looking at sunlight reflecting off it ... what you are then seeing, is some of the  light that the folks who have that smoke between them and the sun are not getting. Smoke will also absorb a lot of sunlight (and re-radiate it as infra-red), especially if it's sooty black smoke rather than whitish ash.</p>

<p>On a gloomy note, you are experiencing what a nuclear war would cause on a global scale (a nuclear winter, caused by the ashes of civilisation). At least your smoke is not radioactive and relatively short-term ....</p>

CC BY-SA 4.0
2020-01-08T10:14:58.267Z
2020-01-08T10:14:58.267Z
nigel222
<p>Saturday 4th January was truly an extroadinary and terrible day for the south-east corner of Australia. Skies turned pitch black at around 3-5 pm, when normally these areas would be in daylight. I have never been aware of this sort of phenomenon. Is it possible that thick smoke alone could have caused this, or was it larger particles such as burnt leaves and bark, picked up by strong updraughts from pyrocumulus clouds? It is worth noting that this occurred right before a cold front passed through the area, bringing southerly winds, and that pyrocumulus clouds had formed, and lightning was being generated from them.</p>

CC BY-SA 4.0
2020-01-07T19:22:48.460Z
Yes, it's perfectly possible for smoke to cause this, though I can only cite first-hand experience as evidence.
jamesqf
CC BY-SA 4.0
2020-01-08T03:55:41.693Z
I'm close to the fires (but not directly impacted). Our skies have been either grey, orange grey, or (on the worst days) deep dark red, with a constant smell of smoke and ash blanketing everything. It's not unsurprising to me that as you get closer to the source of all this the sky would darken even worse than what I've seen.
Robotnik
CC BY-SA 4.0
2020-01-08T04:43:01.870Z
This isn't an answer to your question ("What causes it?"), but historically, you may be interested in [New England's Dark Day](https://en.wikipedia.org/wiki/New_England%27s_Dark_Day), when what is presumed to be a Canadian forest fire in 1780 caused New England's (a USA state south of Canada) sky to turn so dark, candles were needed around noon-time. That occurrence is speculated to be a combination of smoke from the forest fire drifting south, in addition to cloud cover and fog.
Jamin Grey
CC BY-SA 4.0
2020-01-08T05:09:18.843Z
@Jamin Grey: New England is actually a region, composed of six US states: Vermont, New Hampshire, Maine, Massachusetts, Connecticut, and Rhode Island.
jamesqf
CC BY-SA 4.0
2020-01-08T05:35:00.930Z
@jamesqf I'm an USA-born American who've lived my whole in the USA. I'mma go hides my face in shame for just now learning what you explained. =P
Jamin Grey
CC BY-SA 4.0
2020-01-08T11:43:56.150Z
@JaminGrey Obligatory xkcd: [you're one of today's lucky 10.000](https://www.xkcd.com/1053/) (and I'm one of -a bit more of- them too, even if I'm not American ;) )
Rafalon
CC BY-SA 4.0
2020-01-08T18:14:36.263Z
@Jamin Grey: Don't feel too bad.  I'm often confused when people use those stupid two letter state codes, one of which is NE, and my first thought is that they're in New England :-)  And then there's postal CA = California vs internet CA = Canada...
jamesqf
<wildfire><fire>
Why did the Australian bushfires cause pitch darkness during the daytime?
Al2110
# Why did the Australian bushfires cause pitch darkness during the daytime?

(Asked by: username_0 on 2020-01-07)

Saturday 4th January was truly an extroadinary and terrible day for the south-east corner of Australia. Skies turned pitch black at around 3-5 pm, when normally these areas would be in daylight. I have never been aware of this sort of phenomenon. Is it possible that thick smoke alone could have caused this, or was it larger particles such as burnt leaves and bark, picked up by strong updraughts from pyrocumulus clouds? It is worth noting that this occurred right before a cold front passed through the area, bringing southerly winds, and that pyrocumulus clouds had formed, and lightning was being generated from them.

**Tags:** wildfire, fire

> **Comments:**
> **username_1**: Yes, it's perfectly possible for smoke to cause this, though I can only cite first-hand experience as evidence.  
> **username_2**: I'm close to the fires (but not directly impacted). Our skies have been either username_3, orange username_3, or (on the worst days) deep dark red, with a constant smell of smoke and ash blanketing everything. It's not unsurprising to me that as you get closer to the source of all this the sky would darken even worse than what I've seen.  
> **username_3**: This isn't an answer to your question ("What causes it?"), but historically, you may be interested in [New England's Dark Day](https://en.wikipedia.org/wiki/New_England%27s_Dark_Day), when what is presumed to be a Canadian forest fire in 1780 caused New England's (a USA state south of Canada) sky to turn so dark, candles were needed around noon-time. That occurrence is speculated to be a combination of smoke from the forest fire drifting south, in addition to cloud cover and fog.  
> **username_1**: @username_3: New England is actually a region, composed of six US states: Vermont, New Hampshire, Maine, Massachusetts, Connecticut, and Rhode Island.  
> **username_3**: @username_1 I'm an USA-born American who've lived my whole in the USA. I'mma go hides my face in shame for just now learning what you explained. =P  
> **username_4**: @username_3 Obligatory xkcd: [you're one of today's lucky 10.000](https://www.xkcd.com/1053/) (and I'm one of -a bit more of- them too, even if I'm not American ;) )  
> **username_1**: @username_3: Don't feel too bad.  I'm often confused when people use those stupid two letter state codes, one of which is NE, and my first thought is that they're in New England :-)  And then there's postal CA = California vs internet CA = Canada...  

---

## 3 answers

### Answer by username_5 on 2020-01-07. Score: 12

It's a combination of both the density and amount of smoke in the air and [ash](https://www.theguardian.com/australia-news/2020/jan/04/australia-bushfires-week-of-anger-scott-morrison) produced by the fire.

The thing about [cold fronts and bush fires](https://mobile.abc.net.au/news/2019-11-11/fire-weather-and-why-tuesday-looks-so-bad/11693894?pfmredir=sm) is they make the conditions for fire worse by pushing hot air in front of them. They have been blamed for the severity of the bush fires in Victoria in 2009, 1983 and 1939.


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### Answer by username_6 on 2020-01-07. Score: 2

It was a combination of thick smoke and pyrocumulus clouds. Possibly there might have been other types of cloud as well, Ash rising on the updraught may also have been a factor. I am informed that normal types of cloud sometimes made an appearance during the drought. Near-pitch darkness in daylight hours is also characteristic of volcanic eruptions, but I am not suggesting that volcanic eruptions were a factor in this case, though they make an analogy.

During cumulonimbus events in England, usually accompanied by rain and thunder, we often get very dim light in mid afternoon, long before evening time, though I wouldn't describe it as pitch darkness but more a sort of twilight. If enormous plumes of smoke were added, it very likely would have become almost pitch dark.

> **Comments:**
> **username_6**: Not England? Well blow me down, I thought it was one of the southern counties!  
> **username_7**: UK: I remember when the smoke from the Buncefield oil depot explosion/fire drifted overhead, thousands of feet up. It still looked sunny, but it was far too dark.  

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### Answer by username_7 on 2020-01-08. Score: 1

If you think how white smoke looks when it is rising elsewhere and you are looking at sunlight reflecting off it ... what you are then seeing, is some of the light that the folks who have that smoke between them and the sun are not getting. Smoke will also absorb a lot of sunlight (and re-radiate it as infra-red), especially if it's sooty black smoke rather than whitish ash.

On a gloomy note, you are experiencing what a nuclear war would cause on a global scale (a nuclear winter, caused by the ashes of civilisation). At least your smoke is not radioactive and relatively short-term ....


---

