EPW Weather Data Converter

What this tool does

The EPW Weather Converter reads an EnergyPlus Weather (.epw) file — the standard hourly typical-year weather format used by EnergyPlus, OpenStudio, IES-VE, and most building energy simulation software — and turns it into something you can actually look at and work with: a shared-axis temperature chart with daily min/max bands, a searchable hourly data table, and a rolling-window filter for finding extreme periods. It can also fetch real, observed historical weather for a station from Meteostat, so you can compare a "typical year" EPW file against what actually happened in a given year.

What's inside an EPW file

An EPW file starts with 8 header lines (location, design conditions, typical/extreme periods, ground temperatures, holidays, two comment lines, and a data-period declaration), followed by one comma-separated row per hour of the year — 8,760 rows in total. Each row carries 35 fields: dry-bulb and dew-point temperature, relative humidity, atmospheric pressure, wind speed and direction, solar radiation and illuminance components, sky cover, precipitation, and more. This tool parses every field, but focuses its charts and exports on the ones most design workflows actually use — dry-bulb, dew-point, wet-bulb (calculated), and relative humidity.

Typical-year EPW vs. real observed weather

An EPW file is usually a typical meteorological year (TMY) — a synthetic year stitched together from the statistically "most typical" months across a multi-year record, built for consistent simulation, not for representing any single real year. The Meteostat option in the sidebar instead fetches actual recorded hourly observations for a real station and year, pulled from the same open weather-station network Meteostat aggregates from. Switching between the two lets you sanity-check whether a design's typical-year assumptions held up against a specific real year, or investigate an unusually hot, cold, humid, or dry period that an EPW file's averaging would smooth away.

Visualiser, Data, and Filter tabs explained

• Visualiser — a shared-axis line chart of the loaded year, with a shaded daily min/max band so you can see both the hourly trace and the day-to-day spread at a glance.
• Data — the full hourly table underlying the chart, with a column picker and a one-click Excel export of exactly the fields you select.
• Filter — a rolling-window query builder: chain conditions across temperature, humidity, wind, and other fields to isolate matching hours, then see them plotted as a dot plot with longest-streak and peak/trough summaries.

Step-by-step: using the converter

1. Drag and drop an .epw file onto the upload zone, or download one for your region from the links in the sidebar, or switch to Meteostat and fetch a station/year directly.
2. Review the parsed year on the Visualiser tab — the chart and daily bands render immediately.
3. Open Data to browse the raw hourly rows, pick which columns matter to you, and export them to Excel.
4. Open Filter to build a rolling-window query (e.g. "dry-bulb above 32°C for 3+ consecutive hours") and read off the matching periods, longest streak, and peak/trough values.

Frequently asked questions