Temp at Altitude

Hey there......When checking the weather on your program I get Temp forcast of -51c at FL390 which matches real closely. I use it to program the FMC in iFly 737's But when arriving at the Alt the panel shows -25c some times as cool as -35c but never any lower. The aircraft has always been spot on before. It's not big deal doesn't affect anything the weather all seems to be spot with wind and everything else but the Temp. On the ground it is pretty much spot on. Just at the Higher FL's 30's and above.

Thank you, Scooter

I used the REX real weather I got the same thing so I suppose it's working properly.