Olive trees are just starting to become somewhat popular in Central Texas, which runs along that zone line. I planted Aberquine, but there are also some compatible cross pollinators. There a lot of articles online if you do a search for olive trees in central Texas.
Neither of my trees are in a heat trap, and they've both survived two dry cold fronts this winter where very warm weather was followed in hours by several days of very cold weather. We were definitely in the teens for those. Any olive varieties recommended for my area have to be able to handle not just cold weather but extremely fast temperature fluctuations.
What does a metric clock look like? I bet it is nothing like this tiny ad: