Forecast's Pricing 
1,000 API requests per day is free. $1/10,000 API requests after that.
WeatherUnderground's Pricing 
You need to use their pricing calculator, and if you want historical weather, the price goes up a lot. $520/month for 5,000/API requests per day.
Click on some of the WRF-GFS or NAM models. The 'km' denotes the grid size. Scroll down to a precip loop. Voila: tomorrow's weather, today.
Median, or something like trimmed mean.
And, as the service is using the location of the user, why not show the weather in °Celsius, if the region, where the user resides measures in °Celsius (and Fahrenheit, where Fahrenheit is used). I really had to look hard to find the button, to switch.
But non the less, great service, design, that I like, not too much info at first glance, but the most important one, imho.
Living in San Francisco for almost five years, I had to go back to my childhood in Massachusetts to test it. April Fool's day blizzard in Brockton, MA in 1997. Forecast.io shows heavy snow. I got like a week off from school. Works!
[Mind you - it does remember your choice - so its not that bad]
I would like to start a weather forecasting service in my home country, India. Can someone here throw light on how I should go about it? Can I get any ready made softwares into which I can plug in parameters or do I need to understand many technical details and implement my own forecasting programs?
Their summary is odd at times too. My next Monday shows: Icon: cloud with moon, Text: "Partly cloudy overnight.", Details: all clear
The only giveaway when it's running is the address bar at the top.
Android, on the other hand, only has home screen widgets
Regarding the UK, you're right. I'll add a new view that's moved to the west.
or was that more complex?
of course, computing & serving those time point samples might be slightly more complex:)
This is great though, nice one :)
GREAT app btw