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TMY3

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NREL Typical Meteorological Year v3.

At a glance
Original creator National Renewable Energy Laboratory (NREL)
First published 2008
Purpose Typical Meteorological Year, version 3: a year of hourly weather for one US station, with each month taken from the most typical real year for that month.
Extensions .tmy3
Poka parser poka-tmy3
Viewer poka-table-viewer
Depth tier Parser with a shared viewer (see Depth tiers)
Breadth tier B4 Summary (see Breadth tiers)

How much Poka reads

B4 Summary. The container and metadata are read and summarised (counts, properties, structure), but the main content is not rendered.

Confidence: high (the reviewer read the code and a test that proves the claim). Basis: Reviewed 2026-10-16: poka-tmy3 src/lib.rs (parse_tmy3, build_ast, unit tests) and tests/samples.rs; corpus web-723170TYA.tmy3 (Greensboro, 71 columns). TMY3 CSV only. The 8,760 hourly rows are streamed into 12 monthly accumulators and the viewer table has 13 rows (12 months plus a Year row); no hourly row is ever shown.

What Poka does not read

  • individual hourly values (the hourly table is never rendered)
  • dew point and atmospheric pressure are accumulated but not shown in the table
  • extraterrestrial radiation (ETR, ETRN) and diffuse horizontal irradiance (DHI)
  • illuminance fields (global, direct, diffuse, zenith)
  • total and opaque sky cover, visibility and ceiling height
  • present weather codes, precipitable water, aerosol optical depth, snow depth, days since last snowfall, albedo and liquid precipitation
  • wind direction
  • source and uncertainty flags (only the missing-value flag is used)
  • date-ordered or per-day view

Background

Wikipedia describes three TMY editions: the first from 229 US locations (1948 to 1980), TMY2 from 239 stations (1961 to 1990), and TMY3; it cites NREL's User's Manual for TMY3 Data Sets from April 2008. A TMY3 file has two header lines and 8,760 hourly rows of 71 columns. Each month comes from a different real year, so the rows are not in date order and the file has no meaningful date range. Poka shows the station and a monthly summary table (twelve months and a year row, with the year each month was taken from); no hourly row is shown. Hours run 1 to 24.

Versions

Version Identifier Poka Note
TMY3 CSV Partly read All 8,760 rows are read, but only a monthly summary is shown; dew point and pressure are accumulated and never shown.

Libraries

Libraries Poka uses or has assessed for this format, with the status, licence and language the registry records.

  • pvlib-python (pvlib.iotools.read_tmy3) (candidate; BSD-3-Clause; Python; https://github.com/pvlib/pvlib-python) — read_tmy3 loads TMY3 CSV into a pandas DataFrame plus metadata; confirmed on its docs page; needs pandas.

Sources