My comment is a general one.
Engines designed for today's emission sensitive environment are designed to run hot relative to engines designed 10 years ago.
Steps are taken in the engine design to get the catalytic converter or the diesel equivalent up to "operating" temp asap. One of these design steps is to place this emission equipment as close to the exhaust ports as possible.
If Kubota has a section on the temp gauge marked in red or otherwise showing too hot, then trust the designers and try to not worry.
The cooling system will be designed to handle temp environments much hotter than California. Keep the trash screens for the rad clear and all will be fine.
I know Death Valley hit 157F one day in 1913. But when it comes to surface temperature, two spots have Death Valley beat. A new analysis of high-resolution satellite data finds the Lut Desert in Iran and the Sonoran Desert along the Mexican-U.S. border have recently reached a sizzling 80.8°C (177.4°F).
In the design process for any equipment, the test engineers are seeking out extreme climates to validate their calculations.
It is critical that your machine has the recommended 50-50 gylcol water mix and that you ensure this is what you have using a refractometer.
This video will demonstrate:
refractometer
A refractometer can be bought for $20 on amazon.com although as with all test equipment you can spend a lot more
Amazon
Dave