Maybe you can help me out and point out which temperatures you listed can be described as be "harsh"? The American south has summer averages hotter than all of them but I'm yet to hear anyone call Austin's climate "harsh"
Also, the "method" I used is neither very sound nor in any way scientific. Just a very subjective level of comfort for me.
Allow me to add some clarity: I listed the lowest daytime temperature of ANY day of Jan/July, not avg temperature in a month.
According to that method Austin is 9/35.
Sub-25 Celsius is a temperature I find comfortable enough. And looking through the data Austin looks like it's good enough from late October through mid-April, so that's about 5.5 months of nice enough weather in my opinion. But a very hot summer is not something I like.
I'll be spending this winter in Vietnam, not so much for the comfort of it, but to travel and catch up with a few friends that relocated there.