# Clouds disappearing during Solar Eclipse **URL:** \ **Category:** Factual Questions\ **Created:** [August 22, 2017, 3:56pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372 "2017-08-22T15:56:34Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 22, 2017, 3:56pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/1 "2017-08-22T15:56:34Z")
We were in Tennessee for the total eclipse yesterday. In the morning, the sky was completely clear. Towards late morning, a number of cumulus clouds formed in the sky. But as partial eclipse progressed, they all seemed to disappear. The sky was mostly clear for totality. This was contrary to my uninformed expectations - I thought lower temperature would cause _more_ clouds to form. The only explanation we could come up was that the clouds were being fed by thermals (thermal air currents) which died down as the sun dimmed. Is this correct? Or was it just luck? ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [August 22, 2017, 4:18pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/2 "2017-08-22T16:18:18Z")
I’m going with luck … What you started with is a “stable” atmosphere … more stable than could be overcome by the reduction of solar energy … if your atmosphere at the time was much closer to equilibrium, then this reduction of energy would have brought your atmosphere to an unstable state and clouds would have formed (or more probably a low level fog) … in Western Oregon the grass I was lying on started getting wet as though from dew … The OP’s understanding is correct, just that the atmosphere was very stable at the start … the bit of turbulence that cause the cloud to form quickly dissipated … ---
**Author:** ![Pippers](https://avatars.discourse-cdn.com/v4/letter/p/b5a626/32.png) [@Pippers](https://boards.straightdope.com/u/Pippers)\ **Post date:** [August 22, 2017, 4:25pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/3 "2017-08-22T16:25:43Z")
I was in eastern Oregon and the only weather change I noticed was a 7 degree temperature drop. Some other people that were in central Oregon said at their location the wind came up, but then died out as the eclipse ended. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [August 22, 2017, 5:10pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/4 "2017-08-22T17:10:57Z")
It was partly cloudy before, during and afterwards in Little Rock. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [August 22, 2017, 5:15pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/5 "2017-08-22T17:15:04Z")
Eclipses dispersing thin clouds is a documented phenomenon. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [August 22, 2017, 5:38pm UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/6 "2017-08-22T17:38:00Z")
> [@scr4](#): > > Towards late morning, a number of cumulus clouds formed in the sky. Yes: for cumulus clouds, the sequence is: - sun heats the ground - warmed ground heats the air near it - warmed air rises, carrying moisture with it - rising air cools due to decreasing pressure - when dewpoint is reached, moisture forms small droplets that become a cloud > [@](#): > > But as partial eclipse progressed, they all seemed to disappear. Yes: as partial eclipse proceeds, reduction in solar heating interferes with step #1 above. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [August 23, 2017, 12:57am UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/7 "2017-08-23T00:57:39Z")
Where were you? I live in Tennessee and we had pretty scattered cumulus that actually got a little thicker as the eclipse happened. The largest cloud of the day approached the sun about 5 minutes before totality, but it looked like it would miss and it did. The effects of eclipses on weather are pretty minor. What I experienced was that when the sun became about halfway obscured, I felt no temperature change in the shade, but I could stand in the sun and no longer feel it’s searing heat. It felt like it was obscured by a cloud, but it wasn’t. I doubt it was enough to disrupt cloud formation. Also, moisture in the air makes temperature changes come slower, so muggy places like Tennessee probably saw less temperature change than drier locations, but I’d like to see some temperature readings surrounding the eclipse. I really wish I had done some myself, now that I think about it. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [August 23, 2017, 1:16am UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/8 "2017-08-23T01:16:01Z")
Some astronomy books speak of how fair weather clouds will often clear out at sunset (without further explanation). A friend and I reasoned the sun is driving the dynamics that form such clouds and/or the thermals that favor formation o these clouds. I wager the same could be true at totality. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [August 23, 2017, 2:18am UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/9 "2017-08-23T02:18:40Z")
I looked up the temperatures recorded at the Knoxville airport, (which may or may not be near the OP’s location but it’s near me). Partial eclipse started at 1:05, totality was at 2:33, eclipse ended at 3:58. There was a 2 degree drop near totality and 2 more degrees during totality, both of which took a little while to recover. The temperature pattern is more or less identical to Sunday’s and today’s except for that. Other than totality, the eclipse seems to have had no effect on temperature. Oddly, it actually got cloudier at the start of the eclipse and stayed that way until it was over. “FEW” clouds means 1/8 to 2/8 of the sky covered by clouds. “SCT” means 3/8 to 4/8 of the sky covered by clouds. The number after that is altitude in hundreds of feet (so 040 is 4000 feet). It was FEW until right after the eclipse started and went to SCT045. It stayed that was for 3 hours until just about the time the eclipse was over, then went back to being FEW. This didn’t have anything to do with the eclipse, it just coincided with it, but neither the eclipse in general nor the totality seems to have had any effect on cloudiness where I was. ```auto 21 Aug 12:00 pm 84 FEW040 21 Aug 12:05 pm 84 FEW040 21 Aug 12:10 pm 86 FEW040 21 Aug 12:15 pm 86 FEW040 21 Aug 12:20 pm 86 FEW040 21 Aug 12:25 pm 88 FEW040 21 Aug 12:30 pm 90 FEW040 21 Aug 12:35 pm 90 FEW040 21 Aug 12:40 pm 90 FEW040 21 Aug 12:45 pm 88 FEW040 21 Aug 12:50 pm 88 FEW040 21 Aug 12:53 pm 88 FEW040 SCT250 21 Aug 12:55 pm 88 FEW040 21 Aug 1:00 pm 88 FEW040 21 Aug 1:05 pm 88 FEW040 **(eclipse begin)** 21 Aug 1:10 pm 88 FEW040 21 Aug 1:15 pm 88 SCT045 21 Aug 1:20 pm 88 SCT045 21 Aug 1:25 pm 90 SCT045 21 Aug 1:30 pm 88 SCT045 21 Aug 1:35 pm 88 SCT045 21 Aug 1:40 pm 88 SCT045 21 Aug 1:45 pm 88 SCT045 21 Aug 1:50 pm 88 SCT045 21 Aug 1:53 pm 88 SCT045 SCT250 21 Aug 1:55 pm 88 SCT045 21 Aug 2:00 pm 88 SCT045 21 Aug 2:05 pm 88 SCT045 21 Aug 2:10 pm 88 SCT045 21 Aug 2:15 pm 88 SCT045 21 Aug 2:20 pm 88 SCT045 *21 Aug 2:25 pm 86 SCT045 21 Aug 2:30 pm 86 SCT045 21 Aug 2:35 pm 84 SCT045 **(totality at 2:33pm)** 21 Aug 2:40 pm 84 SCT045 21 Aug 2:45 pm 84 SCT045 21 Aug 2:50 pm 84 SCT045 21 Aug 2:53 pm 85 SCT045 SCT250 21 Aug 2:55 pm 84 SCT045 21 Aug 3:00 pm 84 SCT045 21 Aug 3:05 pm 86 SCT045 21 Aug 3:10 pm 86 SCT045 * 21 Aug 3:15 pm 88 SCT045 21 Aug 3:20 pm 88 SCT045 21 Aug 3:25 pm 88 SCT045 21 Aug 3:30 pm 88 SCT045 21 Aug 3:35 pm 88 SCT045 21 Aug 3:40 pm 88 SCT045 21 Aug 3:45 pm 88 SCT045 21 Aug 3:50 pm 90 SCT045 21 Aug 3:53 pm 89 SCT045 SCT250 21 Aug 3:55 pm 88 CLR 21 Aug 4:00 pm 90 CLR **(eclipse end)** 21 Aug 4:05 pm 90 FEW100 21 Aug 4:10 pm 90 FEW100 21 Aug 4:15 pm 90 CLR 21 Aug 4:20 pm 90 FEW100 21 Aug 4:25 pm 90 FEW095 21 Aug 4:30 pm 90 FEW095 21 Aug 4:35 pm 90 FEW045 FEW095 21 Aug 4:40 pm 90 FEW045 FEW095 21 Aug 4:45 pm 90 FEW045 FEW095 21 Aug 4:50 pm 90 FEW045 FEW095 21 Aug 4:53 pm 90 FEW045 FEW095 SCT250 ``` ---
**Author:** ![ka9q](https://avatars.discourse-cdn.com/v4/letter/k/74df32/32.png) [@ka9q](https://boards.straightdope.com/u/ka9q)\ **Post date:** [September 3, 2017, 12:04am UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/10 "2017-09-03T00:04:57Z")
I saw the same phenomenon in Riverton WY, and recorded it on my drone. Here’s the video: [![](https://img.youtube.com/vi/kPtQuliiZeg/maxresdefault.jpg "Eclipse by drone") ](https://www.youtube.com/watch?v=kPtQuliiZeg) My hypothesis is that the loss of solar heat stopped the convection that formed and supported these clouds. A friend suggested that they might then begin to fall, which would take them to a lower, warmer altitude below the condensation point so they’d begin to evaporate. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 3, 2017, 1:56am UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/11 "2017-09-03T01:56:09Z")
A contrary point. In Rochester, NY, the clouds began to roll in after the partial eclipsing started. Viewing was pretty good up until the moment of maximum coverage, at which point the clouds completely covered the sun. ---
**Author:** ![rowrrbazzle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rowrrbazzle/32/414_2.png) [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)\ **Post date:** [September 3, 2017, 2:57am UTC](https://boards.straightdope.com/t/clouds-disappearing-during-solar-eclipse/794372/12 "2017-09-03T02:57:58Z")
Luck. In July 1972 some friends and I drove to Cap-Chat to see the eclipse. Light clouds began to form as the eclipse progressed. They were just light enough to see the Sun through, but not the corona. This year, live TV broadcasts from Carbondale in southern Illinois showed that clouds formed similarly, but heavier.