woodworking bench top warped in heat wave. arrrrrrr

Build a workbench a few months ago, 95% finished
Can be find on my ible page.
Had a heat wave for 5 days,  temperatures above 40 degrees. Broke all recorded records here in Victoria Australia
Water boils at 100 water freezes at 0
Temp in shed must have been at least 55,
Is the bow from bad construction or just heat.
Will it return to its original shape or is it $#@!#$

Picture of woodworking bench top warped in heat wave. arrrrrrr
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