How to know when it’s going to rain

Updated April 13th, 2020.

UPDATE March 2020: Apple likes the forecast.io people so much they bought the company.

UPDATE: forecast.io has changed. It’s still great, but it’s now called darksky.net. Read my new article about darksky.net, written in October 2016.

When it comes to rain, most of us have questions like these:

“Do I have time to walk the dog before it rains?”
“Can I put off cutting the grass until tomorrow?”
“Do I need to carry an umbrella with me all day?”
“Is the rain going to stop soon?”

These are simple yes-no questions, yet the typical weather forecast doesn’t come close to answering them. Instead, they give us the ol’ “40% chance of rain in Santa Monica” routine, with little or no specificity. What are you supposed to do, wear 40% of a raincoat? Wear it 40% of the time? Even if they say “Afternoon showers” that’s not narrowing it down enough– are you going to get wet if you go out to lunch? If you leave work at 4 will you be leaving before, during, or after the rain? These are reasonable questions to ask.

What we need is a forecast that tells us things like “The rain will stop in 20 minutes.” Something like the picture below.

Thankfully, fortunately, someone’s figured out a better way to predict the weather, especially when it comes to rain. The company’s called Forecast.io, and they’ve developed their own “hyperlocal precipitation forecasting system”– and it works. I don’t know how they do it, but it works.

UPDATE October 2016: Forecast.io is now Darksky.net. See my article about Darksky.net and the Darksky app.

(That is, it works if you’re in the United States or in the United Kingdom, or in Ireland. “More coming soon,” they say.)

Forecast.io’s weather predictions focus on precipitation, and especially what’s going to happen in the next hour. They’re confident enough in their predictions to say things like “Rain starting at your location in 10 minutes.” Originally, that’s all they did: predict precipitation for the next hour. Now they’ve expanded into making predictions for the next week. I’ve used Forecast.io’s predictions during Southern California’s recent El Niño storms, as well as during thunderstorm season in Central Texas, and dang if they aren’t pretty close to right on the mark.

Here’s how you can use Forecast.io’s hyperlocal precipitation forecasting system for free.

Go to the www.forecast.io website. Allow the site to use your location– that way, you don’t have to tell them where you are. They’ll figure it out.

On a Mac, Forecast.io’s website looks like this (click for a larger version):

Bookmark the site, add various locations (your hometown, your friend’s place, Dad’s new home in Oregon, etc.), and you’ll always be just a click away from knowing when it’s going to rain. Notice there’s always the “Current Location” option near the top left. No matter where you are, one click provides the local-est weather report you can get.

Also notice that big globe. If you click on it you’ll start an animation. Click the globe again to pause, click again to resume. Click at the top to zoom in for Regional and Local views. It’s a really pretty animation. See the video-capture below. Click it, somebody, please! You have no idea how much work went into capturing that for you.

If you scroll down, Forecast.io’s site looks like this:

Click on a day and it expands to show the details, like this:

Click again to hide the details. Clean, simple, and informative.On an iPhone, Forecast.io’s website looks like a miniature version of what you’d see on a Mac. See below:

It works, but if you follow the steps below you’ll improve the experience significantly. It takes about a minute.First go to forecast.io on your iPhone.

See that black box (outlined above, by me, in red)? Tap it (on your iPhone) and get this:

Follow the directions (I’ve boxed them in red for you) and tap the “Share” button at bottom center of the screen. That leads to this screen:

Tap the “Add to Home Screen” button (you may need to swipe from right to left to get that button to appear), leading to this screen:

Simply tap the “Add” button at top right and you’re done. You’ll be shown your Home screen and the Forecast icon should be right in front of you. Tap that icon and you’re launching a Forecast that fits the iPhone screen perfectly. It’s an entirely different design. It looks like this when you first launch it (be sure to allow Forecast to access your location while you use the app– otherwise, they won’t know where you are):

and it looks like this when you tap the little “NEXT 7 DAYS” tab at the bottom of the screen:

Tap any day to see details. Tap all over the place. Swipe left and right. There’s a lot to explore, and it’s all free, free free.

Actually, it’s not exactly free. Forecast is supported by ads, and you’ll probably tap one by mistake a time or two. Watch for ads sneaking up from the bottom of the screen. They’re a little annoying but you’re getting great information from Forecast, so that’s the trade you have to make. Unless, of course, you’re willing to pay to get an ad-free experience. In that case, you can use any of several apps that tap into Forecast’s data, each with its own way of presenting the forecast, and each a lot more than simply “Forecast.io without ads.” Forecast themselves created a very nice app called Dark Sky, and other developers have created apps such as Check the Weather and Weather Caster. Forecast very helpfully maintains a list of apps (and services) that use their data– here’s a link to the list.

Forecast also offers a free chunk of code that a web developer could use to show real-time, up-to-date weather info, as I’ve done below. Super easy, super fun.

If you haven’t figured it out yet, I really like forecast.io. You should check it out.

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