{{/* Ported from templates/about.html.j2. Extra data: .Breadcrumb.
     temp(60) renders through the request-scoped formatter (no unit scope on
     this page in Python → °F). */}}{{template "base_head_start" .}}{{template "base_head_end" .}}{{template "base_body_start" .}}{{template "breadcrumb" .}}<article class="climate-page">
  <h1>About Thermograph</h1>
  <p class="lede">Thermograph answers one question for any point on Earth: <b>how unusual is this
     weather?</b> Instead of an absolute temperature, it shows where a day falls in that exact
     location's own climate history.</p>

  <h2>Where the data comes from</h2>
  <p>The ~45-year daily record (high, low, feels-like, humidity, wind, gust and precipitation)
     comes from the <b>ERA5 reanalysis</b> (ECMWF), served via <a href="https://open-meteo.com/" rel="nofollow">Open-Meteo</a>.
     Because reanalysis is a gridded, model-consistent record, Thermograph works even where there's
     no weather station, anywhere on the ~4&nbsp;sq&nbsp;mi grid.</p>

  <h2>How a day is graded</h2>
  <p>For each metric and date, Thermograph builds a reference distribution from every historical day
     within <b>&plusmn;7 days of that day-of-year</b>, a 15-day seasonal window across all years. The
     observed value is placed on that distribution as an <a href="{{.Base}}/glossary/percentile">empirical
     percentile</a>, then mapped to a grade from “Below Normal” through “High” to “Near Record”.</p>
  <p>Everything is <b>relative to the location</b>: a {{.Fmt.Temp 60.0}} day can be “Above Normal” in one place and
     “Below Normal” in another. Precipitation is graded only among days that actually rained, so “Heavy”
     means heavy for a rainy day <i>here</i>. See the <a href="{{.Base}}/legend">grade guide</a> for the full scale.</p>

  <h2>Freshness</h2>
  <p>The historical archive updates as new days are added; recent and forecast conditions refresh hourly.
     City climate pages show the latest recorded day graded against the local normal.</p>

  <p><a class="cta" href="{{.Base}}/">Open the weather grader →</a></p>
</article>
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