Defaulting climate pages to the city's temperature convention left every page
half-converted: a Delhi reader got °C next to "9 mph" and "0.00 in". One flag now
drives every measure — picking °C also gives mm and km/h.
Absolute humidity stays g/m³ in both systems; there is no imperial unit for it
anyone would recognise, so converting it would only make the page worse.
units.js becomes the single source for all of it. The formatting logic existed in
three independent copies — shared.js's fmtPrecip/fmtWind/fmtHumid, a second set
inside fmtMetricVal, and a third baked into chart.js's series labels, axis ticks
and tooltip — which is why the units drifted apart in the first place. shared.js
now re-exports from units.js so its importers are unchanged, and chart.js carries
a per-series unit `kind` in place of sniffing for a "°" suffix, which could not
have extended to three unit families.
Server-rendered pages gain the carrier they were missing: precipitation and wind
now render as <span class="precip" data-precip-in> / <span class="wind"
data-wind-mph>, the same contract temperature already had, so climate.js can
repaint them on toggle and the attribute stays imperial as the source of truth.
Precision follows the unit: millimetres get one decimal where inches get two.
0.04 in and 1.0 mm are the same amount, and "1.02 mm" would advertise precision
the source doesn't have. Wind rounds half-up to match Math.round, as temperature
already does.
The weekly table's wind and rain cells are bare numbers to keep the grid narrow,
so their row labels now carry the unit and rebuild per render. Static copy that
names a unit — the legend's "(mph)", "(inches)", and a "(°F)" that had been wrong
for °C readers since the country defaults landed — is marked up with
data-unit-label and painted from the same source.
The chart keeps its imperial domain; only labels convert, so point positions and
the fan geometry are untouched.
Push and email bodies are still imperial-only (notify.py): they are composed
server-side with no client to repaint them and no per-user unit stored, which is
the same limitation temperature already has there. Left for a follow-up.
Claude-Session: https://claude.ai/code/session_013dRZmX9D3JEntfMKWMTWZ8
Search Console shows impressions skewing hard to °C countries — India, South
Africa, New Zealand, the UK, Australia — while every climate page rendered °F
into the HTML. Search snippets quote the server-rendered text, so a reader in
Delhi saw a temperature they had to convert in their head before the page was
worth a click.
Climate pages now render temperatures in the city's country convention: °F for
the US and the handful of other Fahrenheit countries, °C everywhere else. This
happens server-side, so it holds with no JS and shows up in the snippet.
data-temp-f keeps the raw Fahrenheit in every case — it stays the conversion
source of truth, and climate.js repaints from it on toggle exactly as before.
The visitor's stored choice still wins over everything; the page default only
sits between that and the locale guess, so a first-time visitor stops seeing a
°F→°C repaint on load for the majority of our traffic.
The unit rides on a ContextVar rather than a parameter because _temp() is
reached from both directions — templates call it as a Jinja global, and the
context builders call it directly to pre-render the records tables into strings.
Threading an argument would mean touching ~20 call sites across three levels of
nesting, where missing one yields a silently wrong unit instead of an error. The
scope wraps the context builder as well as the render, since the builder is
evaluated as an argument and runs first, and it resets in a finally: the page
handlers are sync `def`, so Starlette runs them on a recycled threadpool thread
and a value left set would leak into the next request that thread serves.
Conversion rounds half-up to match JS's Math.round rather than Python's
round-half-to-even, so the server prints the number climate.js would and there
is no flicker on load for a visitor whose unit already matched.
Pages with no single city — the homepage strip, the hub, the interactive views —
set no scope, emit no data-unit-default, and keep today's locale behaviour.
Precipitation, wind and humidity stay imperial; that inconsistency is worth a
follow-up but is outside this change.
Two existing assertions were passing for the wrong reason: base.html.j2 mentions
"°F/°C" in an HTML comment, so a bare `"°F" in html` check succeeded even on a
page whose every temperature was Celsius. They now read the rendered spans.
Claude-Session: https://claude.ai/code/session_013dRZmX9D3JEntfMKWMTWZ8
The server-rendered SEO pages shared base.html.j2's nav but carried no JS, so
they lacked the °F/°C toggle and account/bell, and their temperatures were baked
as dual-unit strings that couldn't respond to a toggle.
- Load units.js + account.js + climate.js on base.html.j2, so every SEO page gets
the same header as the interactive pages (nav + °F/°C toggle + account + bell).
- Emit each temperature as <span class="temp" data-temp-f> (default °F text, real
for crawlers/no-JS); climate.js rewrites them to the active unit on load and on
toggle. Tint classes stay pinned to absolute °F. Drops the inline "(NN°C)".
- Make account.js base-aware: derive the app base from import.meta.url so its
api/v2 fetches and the alerts links resolve from deep /climate/{slug} URLs
instead of 404ing. Equivalent on the depth-1 interactive pages.
- Default the unit from the browser locale for first-time visitors (no stored
pref): en-US → °F, everyone else → °C. A stored choice always wins.
On phones the header spanned two rows: the title block plus a control bar of
the °F/°C toggle, bell, account and hamburger. Wrap the nav in a .nav-panel
inside the <details> menu and inject the °F/°C toggle and account/bell into that
panel instead of into the header row. On desktop the panel is display:contents,
so the inline top bar renders exactly as before (order restored via flex order);
on phones the panel becomes a right-anchored, viewport-clamped dropdown and the
header collapses to a single row (logo + name + hamburger, tagline hidden).
The viewport clamp also fixes the SEO/city pages, whose menu dropdown previously
ran off-screen.
- Collapse the view navigation into a hamburger menu on phones. The nav is
wrapped in a <details> (pure CSS, no JS — so it works on the crawlable SEO
pages too): transparent (display:contents) on desktop so the tabs render
inline, a dropdown behind a hamburger under 640px. The °F/°C toggle, bell and
account stay in the header bar; units.js/account.js now anchor their injected
controls on the wrapper.
- Replace the header logo: the ▚ glyph was a rotated Unicode char that fonts
rendered inconsistently (warped). Use a crisp inline SVG of the two accent
squares (currentColor) across all headers.
- Month pages: turn the plain "Visiting <city> in <month>?" line into a bordered
callout with a CTA button, matching the city page's travel box.
Verified in Firefox and Chromium at desktop and 390px, light and dark: desktop
nav inline, mobile hamburger opens the dropdown, logo crisp, travel note styled.
compare.js never imported units.js, so the header unit toggle was never
built on the compare page and every temperature was stuck in °F. Import
units.js (which builds the toggle) and route the comfort target, comfort
band, and the colder/warmer/typical-miss figures through the unit
formatters, re-rendering on unit change. State stays in °F (the API's
unit); only the displayed numbers convert.
Add fmtDelta for degree *differences* (band, average miss), which scale
by 5/9 without the 32° offset that absolute temperatures use.
The frontend was classic scripts sharing one global scope, with a
load-order contract enforced only by comments (leaflet -> nav ->
shared -> mappicker -> page) and hand-rolled window.Thermograph /
window.LocationPicker namespaces. Page scripts now import what they use;
the dependency graph replaces the ordering contract, and no app globals
remain (Leaflet stays a classic script / global L, loaded first).
nav.js had grown four concerns; it's now three single-purpose modules:
- nav.js: last-location memory + header view-links + locHash.
- units.js: the °F/°C toggle and unit-aware formatting. The compare
special case is gone — pages that want the toggle import units.js;
compare simply doesn't.
- cache.js: the IndexedDB response cache, SWR getJSON, bundle-seeded
view prefetch and neighbor warming. prefetchViews(lat, lon, ownViews)
now takes the calling page's own view names instead of a page-identity
map (VIEW_OWN) — adding a page no longer means editing this module.
The slice->URL map stays here as bundle-contract knowledge.
frontend/package.json ({"type": "module"}) makes CI's node --check
parse the files as modules.
Verified: node --check on all files as modules; 108 backend tests;
headless-Chromium smoke across all five pages against live data — zero
console/page errors, all render assertions pass (cards, chart, calendar
grid + metric switch, ladders, compare ranking, legend scales).
