I updated the Forecast block. You now have the option to also use DarkSky.net forecasts. No need to set up anything, just update the block files and then in your settings make sure DarkSky is enabled.
Also, in a few hours Im going to Prague to visit my dad, this happens about twice a year and I will therefore not be available to provide support until Sunday. Any issues or emails will be dealt with on Sunday as I will only have limited access to the internet until then.