MOSFET Difference between Normalised On Resistance and Output characteristics
"Normalized" is what you are missing. The Y axis on the RH graph is dimensionless- it's a ratio. 

If the MOSFET has an \$R_{DS(ON)} \$ of 43m\$\Omega \$ at ~27°C, then it will be something like 1.45 times that at 100°C, and 0.6 times that ~=25.8m\$\Omega \$ at -40°C. 

A rough rule of thumb I use is that the datasheet \$R_{DS(ON)} \$ will be about 50% higher at the maximum junction temperature that I'd like to operate at. 
That's because it's usually quoted at a junction temperature of 25°C. They test that by using short pulses of current so the junction doesn't get a chance to heat up. So, like many datasheet numbers, the \$R_{DS(ON)} \$ number in the big print can mislead the unwary.