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Ordinary skies, strange reports, and how UFO sightings get identified.

Within Weather Records

The weather questions Blue Book needed answered

Project Blue Book treated missing weather details as a reason a UFO report could remain impossible to evaluate.

On this page

  • Weather details Blue Book wanted in reports
  • How haze, fog and clouds affected ordinary explanations
  • Why missing conditions can leave cases unresolved
Preview for The weather questions Blue Book needed answered

Introduction

Project Blue Book did not treat weather as a minor detail. For Air Force investigators, weather information was often the difference between identifying a sighting and leaving it unresolved. When a witness reported an unusual light, object or manoeuvre in the sky, investigators needed to know not only what was seen but also the atmospheric conditions through which it was observed. If key weather information was missing, Blue Book could place a case into the category of insufficient information rather than reach a firm conclusion. [Defense Logistics Agency]esd.whs.milDefense Logistics AgencyProject Blue BookThe Air Force groups its evaluations of UFO reports under three general headings: (1) identified…

Blue Book illustration 1 This approach is important in understanding the causes of UFO reports. Many ordinary explanations depended on visibility conditions. A bright planet viewed through haze, an aircraft partly hidden by cloud, or lights distorted by mist could all appear unusual. Without reliable information about clouds, visibility, precipitation or wind, investigators often lacked the evidence needed to test those possibilities. [Wikimedia Commons]upload.wikimedia.orgCommons The Project Blue Book Archive34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (…Read more…

The weather questions Blue Book needed answered

Blue Book developed standardised questionnaires to collect details from witnesses. Weather formed a dedicated part of these forms because investigators considered atmospheric conditions essential to evaluating a report.

The questionnaire asked witnesses to describe:

  • Cloud conditions, including whether the sky was clear, hazy, partly clouded or heavily overcast.
  • Wind conditions, ranging from calm air to strong winds.
  • General weather, including dry conditions, fog, mist, rain or snow.
  • The conditions present at the time the object was first and last observed. [Wikimedia Commons]upload.wikimedia.orgCommons The Project Blue Book Archive34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (…Read more…

These questions were not administrative formalities. They were intended to help investigators compare witness descriptions with known atmospheric and astronomical conditions. Wind information could be compared with balloon movements. Cloud information could reveal whether an object appeared and disappeared behind cloud layers. Fog and mist reports could explain changes in brightness, colour or apparent size. [Wikimedia Commons]upload.wikimedia.orgCommons The Project Blue Book Archive34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (…Read more…

Blue Book investigators also routinely sought supporting meteorological records from weather stations and military facilities when available. The goal was to determine whether the reported behaviour matched ordinary phenomena under the conditions that actually existed at the time. [Wikimedia Commons]upload.wikimedia.orgCommons The Project Blue Book Archive34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (…Read more…

Project Blue Book: America's Obsession with UFOs

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How haze, fog and clouds affected ordinary explanations

A recurring lesson in Blue Book files was that atmospheric conditions could dramatically alter how familiar objects appeared.

Haze and astronomical objects

Blue Book repeatedly encountered reports involving bright planets and stars. Under clear conditions these objects could often be recognised, but haze near the horizon could make them appear larger, coloured, pulsating or mobile. Investigators therefore needed precise information about visibility and cloud cover before ruling out astronomical explanations. [Studocu]studocu.comStudocuUFO Investigations Under Project Blue Book (Feb 1966)The Air Force groups its evaluations of UFO reports under three general headi…

A witness who simply reported a “clear night” might still have been viewing an object through a thin haze layer close to the horizon. From an investigative standpoint, that distinction mattered.

Blue Book illustration 2

Cloud layers and apparent motion

Clouds could create the illusion that a stationary object was moving. An aircraft light seen through broken cloud might seem to dart, stop or change direction as different cloud layers obscured parts of the view. Searchlights and reflections could also produce unusual appearances when interacting with low cloud. [Studocu]studocu.comStudocuUFO Investigations Under Project Blue Book (Feb 1966)The Air Force groups its evaluations of UFO reports under three general headi…

Because of this, Blue Book’s questionnaires sought more than a simple yes-or-no answer about cloudiness. Investigators needed enough detail to reconstruct the witness’s viewing conditions.

Fog, mist and loss of visual reference

Fog and mist reduce contrast and eliminate visual reference points. Under such conditions it becomes harder to judge distance, size and speed. A relatively ordinary light can appear larger, closer or more mysterious than it actually is. Blue Book’s forms specifically asked whether fog, mist or light rain were present because these conditions could significantly affect perception. [Wikimedia Commons]upload.wikimedia.orgCommons The Project Blue Book Archive34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (…Read more…

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Why missing conditions can leave cases unresolved

One of Blue Book’s official categories was not “unidentified” but “insufficient information”. Investigators recognised that some reports simply lacked enough data for a reliable evaluation. Missing weather information was a common reason why this happened. [Defense Logistics Agency]esd.whs.milDefense Logistics AgencyProject Blue BookThe Air Force groups its evaluations of UFO reports under three general headings: (1) identified…

A witness might provide a detailed description of an object yet fail to record:

  • Visibility distance.
  • Cloud height or coverage.
  • Presence of haze or mist.
  • Wind direction and strength.
  • Changes in weather during the observation.

Without those details, investigators could neither confirm nor eliminate many conventional explanations. An unexplained report was not necessarily evidence of something extraordinary; it could reflect the absence of information needed to test ordinary possibilities. This distinction became formalised in Blue Book’s analytical procedures and later statistical studies. [CIA]cia.govANALYSIS OF REPORTS OF UNIDENTIFIED AERIALPROJECT BLUE BOOK SPECIAL REPORT NO. 14 (ANALYSIS OF REPORTS OF UNIDENTIFIED AERIAL OBJECTS) PROJECT NO…. INSUFFICIENT INFORMATION and… [CIA]cia.govSPECIAL REPORT NO. 14. (ANALYSIS OF REPORTS OF UNIDENTIFIED AERIAL OBJECTS). PROJECT NO. 10073. 5 MAY 1955. FOR OFFICIAL USE ONLY. (AFR 1…Published: MAY 1955

The large Battelle Memorial Institute analysis behind Project Blue Book Special Report No. 14 separated cases into identified, unidentified and insufficient-information categories. The existence of the latter category reflected an important methodological principle: investigators preferred admitting that evidence was incomplete rather than claiming certainty where critical facts were missing. [CIA]cia.govCIA RDP81R00560R000100010001 0Air Force Headquarters Monitor of AF Project Blue Book. UFO investigation, prepared analyses of UFO data for AF, liaison officer between…

Blue Book illustration 3

What Blue Book’s weather questions reveal about UFO investigations

The weather section of Blue Book’s reporting system shows how seriously investigators treated environmental conditions. Rather than asking only what an object looked like, they asked what the sky looked like, how clear the air was and whether atmospheric conditions might have influenced perception.

For the broader study of UFO reports, this remains a useful lesson. Many sightings cannot be assessed solely from witness descriptions. Visibility, cloud cover, haze, fog and wind often determine whether a report can be matched to an aircraft, balloon, astronomical object or atmospheric effect. When those details are missing, even a sincere and detailed account may remain unresolved—not because the object was necessarily extraordinary, but because the conditions needed for evaluation were never recorded. [Wikimedia Commons]upload.wikimedia.orgCommons The Project Blue Book Archive34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (…Read more… [Defense Logistics Agency]esd.whs.milDefense Logistics AgencyProject Blue BookThe Air Force groups its evaluations of UFO reports under three general headings: (1) identified…

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Endnotes

  1. Source: cia.gov
    Title: ANALYSIS OF REPORTS OF UNIDENTIFIED AERIAL
    Link: https://www.cia.gov/readingroom/document/cia-rdp81r00560r000100060001-5
    Source snippet

    PROJECT BLUE BOOK SPECIAL REPORT NO. 14 (ANALYSIS OF REPORTS OF UNIDENTIFIED AERIAL OBJECTS) PROJECT NO.... INSUFFICIENT INFORMATION and...

  2. Source: upload.wikimedia.org
    Title: Commons The Project Blue Book Archive
    Link: https://upload.wikimedia.org/wikipedia/commons/5/5c/Project_Blue_Book%2C_BBA-PBSR8-300.pdf
    Source snippet

    34.1 CLOUDS (Circle One) a. Clear sky b. Hazy c. Scattered clouds d. Thick or heavy clouds e. Don't remember. 34.3 WEATHER (...Read more...

  3. Source: studocu.com
    Link: https://www.studocu.com/en-za/document/university-of-the-witwatersrand-johannesburg/physics-for-scientists-engineers-i/ufo-documents-and-information/120714874
    Source snippet

    StudocuUFO Investigations Under Project Blue Book (Feb 1966)The Air Force groups its evaluations of UFO reports under three general headi...

  4. Source: upload.wikimedia.org
    Link: https://upload.wikimedia.org/wikipedia/commons/2/21/Project_Blue_Book%2C_BBA-PBSR11-300.pdf
    Source snippet

    Wikimedia CommonsThe Project Blue Book ArchiveSeptember 9, 2005 — The Project Blue Book Archive contains tens of thousands of documents g...

    Published: September 9, 2005

  5. Source: cia.gov
    Link: https://www.cia.gov/readingroom/docs/CIA-RDP81R00560R000100060001-5.pdf
    Source snippet

    SPECIAL REPORT NO. 14. (ANALYSIS OF REPORTS OF UNIDENTIFIED AERIAL OBJECTS). PROJECT NO. 10073. 5 MAY 1955. FOR OFFICIAL USE ONLY. (AFR 1...

    Published: MAY 1955

  6. Source: cia.gov
    Title: CIA RDP81R00560R000100010001 0
    Link: https://www.cia.gov/readingroom/docs/CIA-RDP81R00560R000100010001-0.pdf
    Source snippet

    Air Force Headquarters Monitor of AF Project Blue Book. UFO investigation, prepared analyses of UFO data for AF, liaison officer between...

  7. Source: upload.wikimedia.org
    Title: Project Blue Book, BBA PBSR1 300
    Link: https://upload.wikimedia.org/wikipedia/commons/3/3b/Project_Blue_Book%2C_BBA-PBSR1-300.pdf
    Source snippet

    Project Blue Book ArchiveThe majority of the [radar]({{ 'radar/' | relative_url }}) sight- ings are very difficult to evaluate due to the possibility of phenomena caused...

  8. Source: esd.whs.mil
    Link: https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%20Room/UFOsandUAPs/proj_b1.pdf?ver=2017-05-22-113513-837
    Source snippet

    Defense Logistics AgencyProject Blue BookThe Air Force groups its evaluations of UFO reports under three general headings: (1) identified...

  9. Source: archives.gov
    Title: Project BLUE BOOK
    Link: https://www.archives.gov/research/military/air-force/ufos
    Source snippet

    Unidentified Flying ObjectsPro-UFO researchers claim that an extraterrestrial spacecraft and its alien occupants were recovered near Rosw...

  10. Source: Wikipedia
    Title: Project Blue Book
    Link: https://en.wikipedia.org/wiki/Project_Blue_Book
    Source snippet

    Project Blue BookProject Blue Book was the code name for the systematic study of unidentified flying objects (UFOs) by the United Stat...

  11. Source: bahaistudies.net
    Title: project blue book
    Link: https://www.bahaistudies.net/asma/project_blue_book.pdf
    Source snippet

    29 Sept 2012 — The Air Force groups its evaluations of UFO reports under three general headings: (1) identified. (2) [insufficient data]({{ 'missing-data/' | relative_url }})...

  12. Source: britannica.com
    Link: https://www.britannica.com/topic/Project-Blue-Book
    Source snippet

    Project Blue Book | Definition, History, Aliens, UFOs, & Facts16 May 2026 — From 1947 to 1969, 12,618 sightings were recorded; of these...

    Published: May 2026

Additional References

  1. Source: cnes-geipan.fr
    Link: https://www.cnes-geipan.fr/sites/default/files/Aids_to_identification_of_flying_objects_0.pdf
    Source snippet

    This report, dated May 5, 1955... There is no direct relationship between the many private. UFO organizations and...Read more...

    Published: May 5, 1955

  2. Source: youtube.com
    Link: https://www.youtube.com/watch?v=Xu4oTBBI5UE

  3. Source: unwritten-record.blogs.archives.gov
    Title: project blue book looking to the film record
    Link: https://unwritten-record.blogs.archives.gov/2013/09/30/project-blue-book-looking-to-the-film-record/
    Source snippet

    Blue Book: Spotting UFOs in the Film Record30 Sept 2013 — By this point, more than fourteen years into Project Blue Book, Quintanilla rep...

  4. Source: docsteach.org
    Link: https://docsteach.org/document/ufo-questionnaire/
    Source snippet

    Air Force's investigations into UFOs. During the Cold War in 1952, fearful that the...Read more...

  5. Source: gutenberg.org
    Link: https://www.gutenberg.org/cache/epub/17346/pg17346-images.html
    Source snippet

    Project GutenbergThe Report on Unidentified Flying ObjectsWe investigated dozens of UFO reports, and read and analyzed several thousand more...

  6. Source: ufotransparency.com
    Title: decade 1970s project blue book [special report 14]({{ ‘report-14/’ | relative_url }}) 1955 pbbsr14
    Link: https://ufotransparency.com/files/decade-1970s-project-blue-book-special-report-14-1955-pbbsr14
    Source snippet

    Air Force...8 May 2026 — The authors declared it 'highly improbable' that any unidentified report... UFO ReportsRoyal Australian Air Fo...

    Published: May 2026

  7. Source: si.edu
    Link: https://www.si.edu/object/siris_sil_259088
    Source snippet

    an analysis of the Air Force project blue book special report...Flying saucers: an analysis of the Air Force project blue book special...

  8. Source: reddit.com
    Title: i built a searchable archive of 5000 project blue
    Link: https://www.reddit.com/r/UFOs/comments/1qepsyf/i_built_a_searchable_archive_of_5000_project_blue/
    Source snippet

    I built a searchable archive of ~5000 Project Blue Book...The document text is selectable/copyable, so you can grab snippets or just dow...

  9. Source: af.mil
    Link: https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104590/unidentified-flying-objects-and-air-force-project-blue-book/
    Source snippet

    With the termination of Project Blue Book, the Air...Read more...

  10. Source: archivesfoundation.org
    Title: 50 years ago government stops investigating ufos
    Link: https://archivesfoundation.org/documents/50-years-ago-government-stops-investigating-ufos/
    Source snippet

    50 Years Ago: Government Stops Investigating UFOsAfter investigations found no evidence of any UFO that was extraterrestrial...

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