Answer · confidence: partial
How are wildfire smoke and volcanic aerosols changing daytime sky color in major cities right now, and how do ground instruments measure that change?
The newest fact is dated July 17, 2026, about three months before October 2026, so the records do not describe current conditions 15. The records show that Canadian wildfire smoke turned skies yellow in New England in July 2026 1 and gave city skies an orange haze, such as in Brattleboro, Vermont 13. Smoke particles absorb blue and violet light and let yellow, orange, and red pass through, and the intensity of the color depends on the smoke's thickness, density, and particle size 23. The records do not address volcanic aerosols or October 2026 skies, but they describe ground instruments: AERONET, a ground-based sun-photometer network, agrees with satellite retrievals of smoke absorption 910, and lidar scans give a vertical profile whose integral yields aerosol optical depth 11.
Checked 2026-10-18. Only documented and supported facts are used.
Dig deeper on this questionSources
[1] supported
Wildfires in Canada caused skies in New England to turn yellow in July 2026, leading to air quality alerts in several Connecticut counties.
"Wildfires in Canada turned New England skies yellow this week, prompting officials to warn sensitive groups and raise air quality alerts, which remain in effect for Fairfield, New Haven, Middlesex and New London counties until Thursday night."Yellow sky, oh my! Why wildfires, weather turn the sky different colors
[2] supported
Smoke particles from wildfires absorb shorter wavelengths of light (blue and violet), allowing longer wavelengths like yellow, orange, and red to pass through, which changes the sky's color.
"During a wildfire, particles in the air, like ash and smoke, absorb colors with shorter wavelengths, which are on the blue and violet end of the spectrum. That leaves colors with longer wavelengths — like yellow, orange and red — passing through."Yellow sky, oh my! Why wildfires, weather turn the sky different colors
[3] supported
The intensity of the orange or red sky color is determined by the thickness, density, and particle size of the smoke.
"The intensity of the color is related to the thickness of the smoke, its density and the size of the smoke particles, according to Argianas."Yellow sky, oh my! Why wildfires, weather turn the sky different colors
[4] supported
In 2023, wildfires in Quebec caused skies across the Northeast to turn bright orange.
"The eerie glow may have reminded you of 2023 when wildfires in Quebec caused skies across the Northeast to turn bright orange."Yellow sky, oh my! Why wildfires, weather turn the sky different colors
[5] supported
The aerosol optical depth (AOD) of brown carbon is a measure of the amount of sunlight prevented from reaching the surface due to smoke.
"The aerosol optical depth (AOD) of brown carbon, as shown in the visualization animation, as wildfire smoke intensity, is a measure of the amount of sunlight that is prevented from reaching the surface due to smoke."NASA SVS | Global Smoke Forecast Visualization (Daily Updated)
[6] supported
Brown carbon represents the organic particulate matter emitted by wildfires within the GEOS-FP model.
"Within GEOS-FP, brown carbon represents the organic particulate matter that is emitted by wildfires."NASA SVS | Global Smoke Forecast Visualization (Daily Updated)
[7] supported
Smoke emitted by wildfires contains particles with a diameter smaller than 2.5 microns (PM2.5), which are small enough to penetrate the lungs and enter the bloodstream.
"In addition to toxic chemicals, smoke emitted by wildfires contains particles with diameter smaller than 2.5 microns (PM2.5). PM2.5 is additionally dangerous to breathe in because the particles are small enough to penetrate the lungs and then enter the bloodstream."NASA SVS | Global Smoke Forecast Visualization (Daily Updated)
[8] documented
NASA’s GEOS-FP system provides near-real-time analyses and forecasts of aerosols twice daily at 00z and 12z UTC.
"NASA’s Goddard Earth Observing System Forward Processing (GEOS-FP) is one such system that provides near-real-time (NRT) analyses and forecasts of aerosols in addition to fields necessary for forecasting the weather twice daily each day at 00z and 12z (midnight and noon UTC, the worldwide time standard)."NASA SVS | Global Smoke Forecast Visualization (Daily Updated)
[9] supported
Satellite-retrieved single-scattering albedo for biomass-burning smoke shows good agreement with AERONET, a ground-based sun-photometer network.
"the corresponding SSA retrievals show good agreement with those from the AERONET."Retrievals of aerosol single‐scattering albedo and effective aerosol layer height for biomass‐burning smoke: Synergy derived from “A‐Train” sensors (2008)
[10] supported
The satellite and ground-based aerosol inversions agreed most closely over biomass burning (smoke-producing) sites in South America and the Sahel.
"Regionally, the agreement between the two inversions was robust over the biomass burning sites of South America, Sahel, Indian subcontinent, and oceanic/coastal sites followed by a reasonable agreement over Northeast Asia."Global assessment of OMI aerosol single‐scattering albedo using ground‐based AERONET inversion (2014)
[11] supported
A LIDAR Range-height Indicator scan yields a vertical profile of extinction, and integrating that profile over height gives the aerosol optical depth.
"The Range-height Indicator (RHI) scan of the LIDAR is then utilized to derive the vertical profile of extinction coefficient, which is integrated with height to obtain the aerosol optical depth (AOD)."Determination of Backscatter-Extinction Coefficient Ratio for LIDAR-Retrieved Aerosol Optical Depth Based on Sunphotometer Data (2010)
[12] supported
Wildfire smoke from Canada has spread haze over major U.S. and Canadian cities, obscuring their skylines from the Great Lakes to the East Coast.
"A thick haze has obscured city skylines from the Great Lakes to the East Coast."Photos Show Wildfire Smoke Engulfing Cities Across the U.S. and Canada
[13] supported
Smoke from Canadian wildfires has changed the color of the daytime sky, producing an orange haze in Brattleboro, Vermont.
"smoke from Canadian wildfires creates an orange haze over the area in Brattleboro, Vermont."Photos Show Wildfire Smoke Engulfing Cities Across the U.S. and Canada
[14] supported
The smoke has left city skies gloomy, though daily life continued under them.
"Yet, as photos show, daily life continued under gloomy skies."Photos Show Wildfire Smoke Engulfing Cities Across the U.S. and Canada
[15] supported
Wildfires raging in Canada have carried smoke and hazardous air to Chicago, Minneapolis, New York City and other cities.
"Wildfires raging in Canada have spread smoke and hazardous air to Chicago, Minneapolis, New York City and beyond."Photos Show Wildfire Smoke Engulfing Cities Across the U.S. and Canada
[16] supported
Officials issued hazardous air quality alerts and health warnings, advising sensitive groups such as children and people with asthma to limit time outdoors.
"Officials are advising sensitive groups, including children and people with asthma, to limit their time outdoors."Photos Show Wildfire Smoke Engulfing Cities Across the U.S. and Canada