No difference

The folklore that "fires rise on full-moon nights"

Linking the full moon to fire is folklore well known on fire and rescue front lines around the world. The sense that "full-moon nights mean more callouts" belongs to the same family as the crime and ER myths: the idea that the moon unsettles people and breeds carelessness and trouble. There is also the simple notion that moonlit nights draw more outdoor activity around open flame. So do fires actually rise on full-moon days? This page checks daily, with fire-service data from two cities.

How the verdict is computed

• The data is daily counts of fires only from two cities' fire-service open data: San Francisco (since 2003, U.S. fire service, NFIRS code 1xx) and London (since 2018, London Fire Brigade, Incident Group = Fire). Non-fire calls (false alarms, rescues) are excluded
• Fire counts have weekday and seasonal patterns (winter heating, summer dryness), so the expected value is the average of the "same weekday × same month," and we compare actual ÷ expected as an index (the same adjustment as the accidents and crime topics)
• Using the lunar phase at each city's local noon, we classify full-moon days (within ±24h of the instant) and new-moon days, and compare each group's mean index against normal (1.00)

See the methodology for the verdict thresholds.

Reading the data carefully

• These are fires the service *attended*, ranging from small to major blazes; not every fire is recorded
• This does not dismiss the front line's "full-moon nights are busy" feeling. The page tests only whether recorded fire counts are visibly higher on calendar full-moon days

Sources

• DataSF — Fire Incidents (San Francisco Fire Department, NFIRS fires only)
• London Datastore — London Fire Brigade Incident Records (UK Open Government Licence, Incident Group = Fire only)
• Moon phase instants computed in-house from Jean Meeus, "Astronomical Algorithms" (UTC)