I was looking for a source to get past weather data (past hour/24 hours). Open Weather Map only provides forecast for free. That's when I found
which provides such data, for free, with up to 500 calls per day.
Temperature, pressure and wind speed are configurable based on the API (and if you want to geek out and use Kelvin for temperature, or Beaufort or knots for wind speed, you can). Precipitations are always in mm as per the API. I could add a conversion to inches if there is interest for it.
Polling interval is configurable between 1 minute and 24 hours.
It also provides wind gusts, UV index, min/max temperatures of the past 24 hours. Repository is here, but recommended installation method is through HPM.
When registering to MeteoMatics, you will receive a username and a password via email. These are the credentials to use, as they don't use API keys.