The Northern Lights Odds 2026-27: data files
Northern Lights Escapes, northernlightsescapes.co.uk/press/

A record of past winters, not a promise for any one night.

Free to quote and republish with a credit and a link to Northern Lights Escapes.

FILES
data.csv: one row per base, start month and stay length (1 to 5 nights). share_of_past_windows_with_a_good_night_pct is the share of past trip windows
  starting in that month with at least one good night; past_windows_counted is how many windows sit behind it; winters_used is the number of winters;
  usable_nights_in_month and nights_in_record_for_month show how many nights had complete data. Shares are printed to 2 decimal places.
data-by-winter.csv: the same shares winter by winter. A blank share means no usable windows. fewer_than_20_windows = yes marks a single winter's month
  that rests on only a few windows; the page leaves those out of its ranges.

DEFINITION
Share of past trip windows (starting in that month) with at least one good night. Good night = at least 2 hours that were dark (sun more than 12 degrees below the horizon), clear (cloud 25% or less, 2 oktas) and active (Kp 2 or more).

DATA CREDITS (each licence requires the credit, and the Modified statement is part of it)
- Abisko cloud: SMHI open data, total cloud cover (parameter 16, hourly), Abisko Aut, quality-controlled archive. Source: SMHI. Licence CC BY 4.0 SE. Modified: selected hours, thresholded and combined with other data.
- Kp: GFZ German Research Centre for Geosciences, Potsdam, Kp index (definitive values), CC BY 4.0, doi:10.5880/Kp.0001. Modified: thresholded. The sunspot column is not used.
- Sun position: NOAA general solar position equations (about 0.1 degree).
- Tromsø cloud: MET Norway, hourly total cloud cover in oktas (cloud_area_fraction), downloaded from the MET Norway Frost API (frost.met.no). Licence CC BY 4.0. Modified: selected hours, oktas converted to percent, thresholded and combined with other data.
- Rovaniemi cloud: Finnish Meteorological Institute (FMI) open data, hourly total cloud cover in oktas (TotalCloudCover), downloaded from the FMI open data WFS service (opendata.fmi.fi). Licence CC BY 4.0. Modified: selected hours, oktas converted to percent, thresholded and combined with other data.
- Saariselkä cloud: Finnish Meteorological Institute (FMI) open data, hourly total cloud cover in oktas (TotalCloudCover), downloaded from the FMI open data WFS service (opendata.fmi.fi). Licence CC BY 4.0. Modified: selected hours, oktas converted to percent, thresholded and combined with other data.

CAVEATS
- Kp is a planet-wide index. Kp 2 or more marks a night with some geomagnetic activity. It is not a sighting record, and we do not claim how bright the aurora was.
- Past windows describe the past. They are not a forecast for any given trip.
- A record of past winters, not a promise for any one night.