- Fork this val 👉 https://val.town/v/stevekrouse.umbrellaReminder/fork
- Customize the
location(line 8). You can supply any free-form description of a location.
⚠️ Only works for US-based locations (where weather.gov covers).
- Geocodes an free-form description of a location to latitude and longitude – @stevekrouse.nominatimSearch
- Converts a latitude and longitude to weather.gov grid – @stevekrouse.weatherGovGrid
- Gets the hourly forecast for that grid
- Filters the forecast for periods that are today and >30% chance of rain
- If there are any, it formats them appropriately, and sends me an email
Readme
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import { email } from "https://esm.town/v/std/email?v=9";
import { fetchJSON } from "https://esm.town/v/stevekrouse/fetchJSON";
import { nominatimSearch } from "https://esm.town/v/stevekrouse/nominatimSearch";
import { weatherGovGrid } from "https://esm.town/v/stevekrouse/weatherGovGrid";
export const umbrellaReminder = async (arg) => {
if (arg.method) return Response.json("");
let location = "prospect heights, brooklyn"; // <---- customize this line
let [{ lat, lon }] = await nominatimSearch({
q: location,
});
let { properties: grid } = await weatherGovGrid({
lat,
lon,
});
let { properties: { periods } } = await fetchJSON(
grid.forecastHourly,
);
let { DateTime } = await import("npm:luxon");
let parse = (iso) => DateTime.fromISO(iso).setZone(grid.timeZone);
let today = periods.filter((x) =>
parse(x.startTime).toLocaleString()
=== DateTime.now().setZone(grid.timeZone).toLocaleString()
);
if (today.every((x) => x.probabilityOfPrecipitation.value < 30))
return today;
let format = (iso) => parse(iso).toFormat("ha").toLowerCase();
let html = `The probabilities of rain in <b>${location}</b> today:<br><br>`
+ today.map((
{ startTime, endTime, probabilityOfPrecipitation: { value: p } },
) => `${format(startTime)}-${format(endTime)}: ${p}%`).join("<br>");
return email({ html, subject: "☔️ Carry an umbrella today!" });
};
👆 This is a val. Vals are TypeScript snippets of code, written in the browser and run on our servers. Create scheduled functions, email yourself, and persist small pieces of data — all from the browser.
Comments
There are a lot of lookups here that can be cached:
- Getting your lat, lon could be done once and cached
- Getting your weather.gov grid could also be done infrequently and cached
However, this val only runs once per day, and it doesn't really matter if it takes 500ms or 900ms.
The hardest part of this val was getting all the date manipulation (parsing, formatting, checking for today) to happen in the timezone of the location you're working with.
It was a big upgrade when I switched from JS Date to Luxon. It's convenient that the weatherGov library gives you a timezone!