Certainly is cold high in the Martian atmosphere. The NASA/CalTech graphic above gives us a global temperature profile at 16 miles / 25.7 km. The temperatures presented are in Fahrenheit so to make sense of it the scale to the right ranges from -53.3 C to -153.3 C. The marker indicating where InSight will touch down is in the -73 C to -93 C.
I saw a press conference yesterday and I believe they said the surface temperature at the landing site was gong to be around -4 F / -20 C, I could be mistaken however. If I can find a video of the press conference I will post it. The press conference was quite interesting and they talked about the MarCo CubeSats too – those things are cool even cooler than even I thought!
Here’s NASA’s caption: This map shows the temperature of the Martian atmosphere 16 miles above the surface. The data was taken on Nov. 18, 2018, about one week before NASA’s InSight lander is scheduled to touchdown on the Martian surface. The temperature indicates to mission scientists the amount of dust activity in the atmosphere. The map shows a range of latitudes, with temperatures clearly dropping near the planet’s north pole. The landing locations of various NASA Mars landers are shown for context.