Why are the temperatures wrong?

Flowx shows the raw data from weather simulations. These global simulations are unable to resolve finer details at ground level, which can lead to a bias error in temperature. This bias is usually corrected using a technique called Model Output Statistics (MOS) and this is what you see in 99% of other weather apps. The disadvantage of MOS is that it is restricted to point locations where weather stations exist (airports, towns and cities), so you loose the spatial view of large weather systems. One day we would like to include MOS results in Flowx.

See the wikipedia on MOS for more details.