It's already baking[0,1], so I'm not sure why they include "about to" in the title.
[0] - https://archive.fo/CrVBV
[1] - https://archive.fo/UfS4A
[0] - https://archive.fo/CrVBV
[1] - https://archive.fo/UfS4A
I think it's because we aren't there yet, so baking is probably a relative term. Also the title refers to the heat wave specifically and doesn't say that it's not already unusually warm.