I will be interested to hear how the 0W-20 oil affects your MPG.
I have found that the temperature can really affect my fuel economy. This time of year you may still be buying a "winter blend" gasoline which also has a negative impact.
There are so many other factors that can affect your MPG:
How long is your typical drive? - cold starts always hurt.
Cruising speeds over 55 mph
always reduce your mpg.
As you mention, windy conditions hurt too.
How hilly is your typical drive? - even slight grades have a huge impact on fuel consumption.
With a little more experience and milder weather I'm sure you will get up into the mid to high 40's (or possibly even higher).
One final tip:
Learn to read the assist/regen display to optimize the ability of the car to "glide". Contrary to a conventional car, you will sometimes want to apply slight pressure to the gas pedal to eliminate unneeded regeneration "drag". The design of the engine and the electronic throttle means that sometimes you are not actually using any fuel even when you are lightly pressing on the gas pedal. The iFCD will confirm this if it 'pegs' at 100 mpg (or 0L/100 km). When the engine actually "refires" you should feel a slight lurch and see the fuel display drop suddenly. This takes some practice but will become second nature if you're willing try it.
Enjoy your car!!