stlouis-pollen

JSON API, Prometheus metrics, and MCP server for the St. Louis County pollen & mold count, with historical data back to March 2000. Runs on Cloudflare Workers.

Base URLs:

• https://stlouis-pollen.maxhogan.dev

• https://stlouis-pollen.pmaxhogan.workers.dev

No auth, no tokens. Please be gentle: responses are highly cacheable and rate-limited to 60 requests/minute/IP.

HTTP API

Examples

curl https://stlouis-pollen.maxhogan.dev/today
# {"reportDate":"2026-07-31T05:00:00.000Z","tree":"","treeLevel":null,
#  "grass":"Low","grassLevel":1,"weed":"Moderate","weedLevel":2,
#  "mold":"Moderate","moldLevel":2}

curl https://stlouis-pollen.maxhogan.dev/day/2026-07-30
# {"date":"2026-07-30","available":true,"targetId":13634,
#  "tree":{"count":0,"level":"Absent","levelValue":0}, ...,
#  "species":{"tree":[{"name":"Ash","count":0,"level":"Absent"}, ...]}}

curl "https://stlouis-pollen.maxhogan.dev/history?start=2025-04-01&end=2025-04-30"
# {"start":"2025-04-01","end":"2025-04-30","days":[
#   {"date":"2025-04-01","available":true,"tree":{"count":905,"level":"High",...}, ...},
#   {"date":"2025-04-05","available":false,"reason":"no-report"}, ...]}

Days with no published report return available: false with a reason:

• no-report — proven report-free (weekends, holidays, skipped days)

• not-yet-published — the date is newer than the newest published report

• unknown — couldn't be resolved this request (rare; retry)

Related MCP server: SNOTEL MCP Server

MCP server

Model Context Protocol server over Streamable HTTP (plus legacy SSE at /sse). No auth required.

https://stlouis-pollen.maxhogan.dev/mcp

Claude Code:

claude mcp add --transport http stlouis-pollen https://stlouis-pollen.maxhogan.dev/mcp

Claude.ai / Claude Desktop: add a custom connector with the URL above.

Tools

Data notes

• Source: scraped from the county's Pollen and Mold Center. All data belongs to the Saint Louis County Department of Public Health.

• Cadence: reports are published on weekdays only, usually by ~noon US Central, and some days are skipped entirely. Dates are US Central.

• Coverage: daily reports back to 2000-03-03.

• Levels: the headline tree/grass/weed/mold levels are the summed category counts mapped through the standard NAB scale (Absent=0, Low=1, Moderate=2, High=3, Very High=4), which matches how the county site derives its home-page levels. Per-species levels are reported as printed.

• Immutability & caching: past days are never revised upstream, so they are cached permanently (Workers KV, bundled per month) and served with long/immutable cache headers. Cold historical queries scrape the county site day-by-day (Pollen_Day.aspx?TargetID=N); warm ones never touch it.

How the historical scrape works

The county site keys daily reports by a sequential TargetID (one per published report, monotonically increasing with date). There is no direct date→ID endpoint, so this worker:

1. ships a static table of ~80 (TargetID, date) anchor pairs,

2. resolves a date to an ID with an interpolation search between anchors (each probe is a full day page, so probes double as cache fills),

3. walks IDs forward to cover a range, proving skipped dates report-free when consecutive IDs bracket them,

4. memoizes every discovered pair and day to KV — searches get cheaper forever.

Free-tier KV budget: ~317 month-bundle keys exist in total; each is written only while it fills and then never again, so lifetime writes are bounded by the amount of history (≪ the 1,000 writes/day free limit) and reads are ≤3 per request.

Development

npm install
npm test          # parser unit tests against saved fixtures
npm run typecheck
npm run dev       # wrangler dev

Deploys happen automatically on push to main via the Cloudflare Workers native GitHub integration (Workers Builds). wrangler.jsonc is the source of truth for the custom domain, the workers.dev route, KV, Durable Object, and rate-limit bindings.

License

MIT. Not affiliated with St. Louis County — data is theirs; please attribute it to the Saint Louis County Pollen and Mold Center.