Also true for California for quite some time.
https://www.canarymedia.com/articles/solar/california-solar-...
What's going to happen in the future is that May will be a month of extreme electricity abundance, with a good chunk of the electricity just not being collected at all because the grid doesn't need it, and it will be cheaper to have unused electricity in May than to have too little solar in December.
And eventually that arbitrage will be big enough to justify a pumped hydro/gravity/iron-air storage.