It will be about 10C here today, still and sunny but that is not warm enough to be naked in the yard for me. Ideally needs to be around 20C for me to start to be naked, once it is hotter than 30C it's not as pleasant in the sun but nice to be naked in the shade.
I think it was only 17-18C last week when I was able to get some nude sun time in my yard. It was pre-equinox so the sun did not have much heat but it was nice to get that sun drenched feeling. I thought it had to be 20+ for me to get naked but not so, I couldn't wait.
I'm a low-80's kind of guy.
My wife though is a bit of a "heat-worshipper" so she loves being nude in 90+ temperatures. It's probably in part due to her being a lifelong Midwesterner, where really hot days only last a couple of months.
We had 17C (63F) yesterday and little wind. Now I'm regretting I didn't brave a trip to the beach to experience it on a mild midwinter's Melbourne day. Showers and clouds about today and the warmth won't be hanging around. :-(
I'm now finding at the end of winter or into spring, anything above around 15c is enough to strip off. I have a protected yard from both neighbours & most wind so I can find a sheltered / warm spot. This spring has been cooler than normal and very rainy so any warmth or sun entices me outside. The heater is set on 21-22c and that is warm enough to be nude.