You probably are. Luckily, 15 minutes isn't too bad.
When I worked for a German company, we'd fly German colleagues out for important planning seasons (held over two - three weeks to justify the jet lag).
And we'd always warn those on their first trip about the NZ sun being considerably more fierce than any sun they were used to, yes, far more fierce than Lanzarote, Corsica, or "Blauhimmel Deutschland" (Blue sky Germany) aka the parts of Mallorca that sold Die Welt in local shops, and hotels that served white sausage and wheat beer on Sundays.
And invariably, they thought we were exaggerating, after all it was spring/autumn! They'd go spend a day at Sumner or New Brighton beaches, and then we got to watch their very red faces peel and gradually heal over the next fortnight. Our CEO managed to get sufficiently sunburnt on his first trip that his forehead blistered, which made it hard to maintain eye contact at times.
(He also managed to be on the New Brighton pier during the big Valentine's Day aftershock, which put a charge up him).
They always remembered to wear sunscreen and sun hats on their second trip ...
...conversely, it was lovely for me when I traveled to Germany in their summer, I could have a lunch outside for an hour, and not get burnt. My people are very much of the north.
I spent about 15 minutes under the south island sun without a hat today, and I'm kind of worried I'm sunburnt.