Show HN: SF Microclimates

Why It Matters

Hyper‑local weather data enables more accurate decision‑making for businesses, developers, and AI services that rely on real‑time environmental context. It also demonstrates a scalable, community‑driven model for city‑specific sensor integration.

Key Takeaways

• Free, no‑key API delivers hyper‑local SF weather data
• Covers 50 neighborhoods using 150+ PurpleAir sensors
• Includes real‑time temperature, humidity, and AQI metrics
• Easy integration for AI agents, bots, and home automation
• Open‑source, self‑hostable for other cities’ microclimates

Pulse Analysis

San Francisco’s reputation for dramatic microclimates has long frustrated residents and developers who rely on generic weather feeds. Traditional services report a single temperature for the entire city, masking stark differences between neighborhoods such as the foggy Outer Sunset and the sunny Mission District. The new SF Microclimates API solves this gap by pulling data from more than 150 PurpleAir sensors, aggregating readings into neighborhood‑level averages for temperature, humidity, and air quality. This granular approach gives users a true picture of local conditions, improving everything from commute planning to outdoor event coordination.

From a technical standpoint, the API is built on Cloudflare Workers and leverages a KV cache to deliver near‑instant responses while respecting rate limits. Endpoints include a full‑city dump, single‑neighborhood queries, and a list of available districts, all accessible without authentication. The response format mirrors industry standards, providing ISO‑8601 timestamps, PM2.5 concentrations, and EPA‑derived AQI categories. Because the codebase is open‑source under an MIT license, developers can self‑host, modify bounding boxes, or replicate the model for other cities with distinct microclimates, extending the platform’s utility beyond San Francisco.

For businesses, the API opens new revenue and efficiency opportunities. AI assistants can answer location‑specific weather questions, home‑automation systems can trigger heating or ventilation based on actual neighborhood conditions, and travel apps can offer tourists precise forecasts. Moreover, the inclusion of real‑time air‑quality data supports health‑focused services and compliance monitoring. As cities increasingly adopt sensor networks, the SF Microclimates model illustrates a replicable blueprint for turning raw environmental data into actionable, developer‑friendly APIs that drive smarter products and services.