Thanks 'Engines' always an 'old faithful' of brill info :-)
Billie Flynn Canuckian F-35 Test Pilot quoted in AirForces Monthly Magazine July 2014 which was reproducing a Canadian Skies magazine article:
"...The F-35 is designed to operate from the extremes of 55C [131F] down to well below -40C [-40F]...."
US Mil Spec Hot day was 32.1C, 1013Mb. — UK Hot Day 35.5C, 992Mb.
Development of the Shipborne Rolling Vertical Landing (SRVL) Manoeuvre for the F-35B Aircraft
"(footnote page 4)...Ambient Temperature: 35.5ºC and Pressure: 992mb..."
https://vtol.org/store/product/devel...craft-9024.cfm