Chem Discussion

When iron rusts , 2 things must be around : oxgen & water . Since in Sahara desert always the humidity is very low so rusting is also going very slowly even at high heat . Hong Kong is very wet with a lot of rain & humid air from the seas & ocean bring in moisture to accerate the rusting . Also the wet air contains high % of chloride ions which aid iron rust faster .

How about the temperature?
It will also increase the rate of rusting. The higher the temp., the higher the rate of rusting.