Measured shine.
carwashindex answers one question, wash or wait?, with weather physics instead of guesswork. It's a free tool, not a media site: no login, no cookies, no tracking, no paywall.
What it does
Every wash is a small bet against the sky. Wash before rain and you've paid for nothing; wash in frost and you've frozen your door seals; wash at noon in July and you've traded dirt for water spots. The index reads 7 days of hourly forecast for your exact location and prices that bet: a 0–100 score, a clear WASH / BORDERLINE / WAIT verdict, your best 2-hour window today and tomorrow, a 7-day outlook, and how many dry days the wash would actually hold.
How the verdict is reached
Each forecast hour starts at 100 and takes published penalties: rain probability now, rain arriving within the following six hours, actual precipitation, freezing or extreme heat, high humidity, strong gusts, airborne dust and peak pollen. Scores of 70+ read WASH, 45–69 BORDERLINE, under 45 WAIT. The whole penalty table sits openly on the forecast page; there is no black box and no hand-tuning. Scoring always runs in metric internally, so switching your display units never changes a verdict.
Two things most wash tools skip:
- The look-ahead. A clear sky now is worthless if rain lands in three hours. Every hour is penalised for rain within its following six hours.
- The hold. The index counts the dry hours ahead and tells you how long a wash would last. "A wash now holds 4 days" is a different decision than "holds half a day."
Data sources
- Open-Meteo — hourly weather forecast (rain probability, precipitation, temperature, humidity, wind) and air quality (dust, six pollen species). Free, open, no account required.
- Open-Meteo Geocoding — turning your city search into coordinates. If you use the "my location" button, coordinates are read by your browser and rounded to ~1 km before any request leaves your device.
Air-quality coverage varies by region; where pollen or dust data doesn't exist, the index says so honestly instead of inventing numbers.
Principles
- Free means free. No login, no paywall, no "premium verdict."
- Local-first. Your saved location, units and last forecast live in your browser's storage, not on a server. There are no accounts to breach.
- No tracking. No cookies, no analytics scripts, no fingerprinting. The privacy note is short because there's little to disclose.
- Honest numbers. Confidence reflects real forecast steadiness; missing data reads "no data," never a made-up value.
Who's behind it
carwashindex is a drivenerve tool: part of a family of free, precision web tools for drivers, from track-day cost calculators to build analyzers. Same forge, same rules: numbers first, no dark patterns. Find the rest at drivenerve.com, or say hello via the contact page.