My Dad, a retired physicist, has kindly been calculating when we might have enough sun to start solar cooking this year. Here's what he's come up with:
I don't understand it in the slightest.
Luckily he's also provided a translation:
In Wellington, prime solar cooking days (when we're at a 45 degree angle to the sun, or greater, for 4 hours or more) will begin in mid October, and run through till early March.
Solar cooking is, however, often also possible a few weeks before and after that prime period, so I'm planning to have a go towards the end of September.
The further north you are in New Zealand, the earlier you can start. That means Aucklanders can get in there about a week and half before Wellingtonians, while Mainlanders will have a few more days to wait.
Hurry up, spring!