You can generally solve seasonal shortfalls cheaply by simply adding more solar / wind until you no longer have a seasonal shortfall just a massive surplus in a different part of the year.

Put another way if you want to store power say 1GWh for the worst month, well a solar panel provides a lot of power over even the worst month. 20MW of solar panel averaging even 40MWh/day * 30 days = 1.2GWh and cost way less than 1GWh of batteries.

Near the arctic circle Wind fill the same niche.