Not even half way to boiling really. Although it refers to Europe, it is using farenheit as its scale, as it is a US based publication.
Although for that reason temperature measurements should always include the type for reference.
"Halfway" from where?
Freezing (0C). Halfway through the liquid phase of water. Seems like an at-least-somewhat reasonable starting point.
Halfway from 0°C, the freezing point of water.
0? To 100?
It also depends on the altitude. At a high enough altitude it would be boiling.
It's an important point that multiplying and dividing temperatures in F or C makes no sense. Some people are somehow assuming half way from freezing which is arbitrary. Would a F user assume it means half way from 32F or 0F?
Even with Celsius, perhaps not impossible at the right altitude, low convection, and with a dark color for better radiative absorption.