Smoke Pall of September 1950

Seventy-five years ago on September 24, 1950, the sky over much of the Great Lakes and Mid Atlantic regions went dark. Day turned to night. Many thought the world was ending, but the culprit was smoke from a large wildfire in Canada. Today I will dive into how the Smoke Pall of 1950 brought nighttime to the middle of the day here in Pennsylvania.

Background

I first discovered this event while scouring the Storm Data Publications while doing tornado research. A 'storm report' from September 24, 1950 caught my attention. It wasn't a thunderstorm or a tornado, but smoke. The report stated that a pedestrian was struck and killed by a car in pitch blackness during daytime hours caused by wildfire smoke. The report comes from Tyrone (Blair County), not far from where I live.

List of storm reports from the Climatological Data National Data for September 1950. Report from Tyrone highlighted.

Front page article from the Tyrone Daily Herald September 25, 1950.

The source of the smoke was a large wildfire known as the Chinchaga Fire which started on June 1. The fire burned an estimated 3.5 million to 4.2 million acres in northern British Columbia and Alberta and was finally extinguished in late October. This region was warm and dry in September thanks to a stationary ridge which allowed for the fire to expand rapidly. Due to the remoteness, the fire did not pose a threat to human settlements and therefore was left to burn uncontrolled.

When I first read the report of the pedestrian fatality I thought back to the recent wildfire smoke events that impacted Pennsylvania with limited visibility and poor air quality, mainly the smoke events in June 2023. The smoke event in 1950 was different, as the smoke was overhead and not at ground level thanks to an inversion. Pilots over Pennsylvania reported that the base of the smoke layer was approximately 12,000 to 14,000 feet above ground level on the 24th. The smoke layer was over a mile tall with reports of smoke up to at least 25,000 feet.

Radiosonde profiles from Pittsburgh on 9/24/1950 and Washington DC on 9/27/1950 (left) and a summarized map of the smoke layer in relation to the fire (right). From Monthly Weather Review, September 1950.

Although the smoke had covered much of the eastern CONUS, the area that observed total darkness was along a swath from north of Lake Superior, through Michigan and down into Pennsylvania. The smoke continued on past North America as it was reported overhead in Europe by the 26th.

Not being able to smell the smoke caused some confusion. With the recent invention of the Atomic bomb, there was fear that the world was coming to an end. Newspapers reported that phone lines were flooded as people were trying to figure out what was happening. Radio was used as a quick and efficient source of spreading word of what was happening.

Smoke Timeline & Descriptions

The first reports of smoke overhead in Pennsylvania were noted as early as 9:30AM on the 24th with most locations seeing the smoke layer by early afternoon. The thickest smoke layer that caused total darkness first moved into the Erie area around 2PM and progressed into southeastern Pennsylvania by around 5:30PM. At this pace the smoke raced across the state at roughly 60mph and complete darkness lasted 1.5 to 2 hours.

Timing of the onset of complete darkness as the smoke pall moved across

Pennsylvania on September 24, 1950. Times are approximate.

Street lights were turned on and headlights on cars were needed in the middle of the afternoon. Stadium lights were turned on at 2:15pm for the Pittsburgh Pirates game versus the Cincinnati Reds in Pittsburgh. Likewise, the floodlights were needed for a football game in Erie. One weather observer in Bradford County noted that "birds and chickens went to roost, cows returned to barns from fields."

Front page of the Bradford Era on September 25, 1950

The descriptions of the sky conditions over the state provide detailed descriptions of the unprecedented event. A wide variety of colors in the sky ranging from yellow to blue to purple and lavender were most commonly reported. Other colors used to describe the spectacle include pink, orange, gray, and bronze. Below are some of the descriptions from COOP weather observers.

"The colors were beautiful as they changed blue-purple to orange"
- Mapleton Depot

"Heaviest overcast in history" - Kane

"The sky became overcast by a pinkish color changing to a slate gray blue and became dark as night..."
- Ridgway

"The intermittent yellow & purple colors in the sky preceded and followed the extreme darkness." - Williamsburg

"Moon and Sun rose like a misty ball. Changed from pink to lavender to purple. Sky streaked with gray and yellow"
- Bethlehem

"The sun was invisible." - Saltsburg

One example of the handwritten weather observation notes describing the smoke pall. This one is from Ridgway.

The observer in Derry (Westmoreland County) slightly misinterpreted the cause of the color in the sky saying that "Strange glow in sky. Said to be reflection of Canadian forest fires."

Weather Impacts

Along with the northwest flow that brought the smoke came cooler than average temperatures with widespread frost on the morning of the 24th. There were even a few reports of snow flurries in northern Pennsylvania, including a trace of snow on the roofs reported in Rew (McKean County) at 6AM. On top of the cool northerly flow, the lack of sunshine kept temperatures cool during the day. High temperatures were in the low to mid 40s in some locations.

High & low temperatures for September 24, 1950, along with locations where snow was reported. Data via SC ACIS and Climatological Data Pennsylvania.

For many observing stations in the state, September 24, 1950, still ranks as one of the coldest high temperatures for the month of September on record. Average temperatures for the period September 24 to September 30 were 8 degrees below average in much of south central and southeast Pennsylvania (when compared to the 1991-2020 average).

Average temperature departure for September 24-30, 1950

(compared to the 1991-2020 average). Map created via Cli-MATE.

The smoke had cleared out of the western half of Pennsylvania on the next day. Weather observers in Burgettstown, Greenville, and Johnstown reported that the partial lunar eclipse on the following evening (September 25, 1950) was visible. The Climatological Summary National Data for September 1950 includes a chart of percentage of clear sky for the month. The values over Pennsylvania indicate that the sky was only clear for about 20% to 40% of the month.

Percentage of clear sky for the month of September 1950.

Map from Monthly Weather Review, September 1950.

Smoke lingered overhead through September 30 across central and eastern Pennsylvania as it got cut off from the main flow. Although not as dark as night the smoke diminished the sunlight. The Pennsylvania Climatological Data summary for the month noted that it was as if the sun rose 1-2 hours later and set 1-2 hours early. The weather observer in the York County community of Wellsville commented, "Sun a pale bluish disk only visible an hour or so daily 9/24-9/30."

Lock Haven Express article from September 28, 1950

The prolonged reduction in sunshine caused crops that were just about to be harvested to stop maturing. In Hawley the weather observations included a note that "most tomatoes blighted from lack of sunshine." "Corn crop late- doubtful if much will ripen. Buckwheat poor," read the remarks from Titusville. The return of sunshine was much welcomed as the Wernersville observer wrote, "Late PM of 30th sun shone brighter than any time during the past 7 days."

Wrapping Up

The Smoke Pall of September 1950 was a memorable sight to see for those who were able to witness this unworldly event. As we saw in 2023, wildfires have been burning larger and more frequently in recent years. It certainly is possible that under the right conditions we may see daytime turn to dark in the not so distant future, just like it did in September 1950.

This was a fun blog to put together, but took a lot of work. Consider subscribing to email alerts when new posts like this one become available. Also, check out the sources below for further reading. I have compiled many newspaper clippings and weather observations for easier access.

Thanks for reading, and remember to always look up!