It is true that diesel fuel has a seasonal blend to ensure the wax doesnt crystallize during the winter periods.
This can be avoided using serveral methods.
a) Create a new blend of diesel, and mix it with a normal summer diesel to reduce the cloud point. This way reduces the power and economy, and is expensive for fuel companies.
b) Use a wax-modifying additive to stop the wax from crystallizing.
This is why I use Millers Diesel Sport 4 in winter to increase the cetane number which improves low-temp combustion, i've filled up yesterday without DPS4 using Shell Extra and I can't believe how rough my engine is in a morning now.