left pad temperature in system tray with spaces

As the temperature changes throughout the day, the number of digits displayed for the temperature in the system tray changes. This causes your entire panel to jump around and you are wondering, did an application crash and a window disappear or did the temperature just change? For the clock we have numbers ranging from 00 to 23 and 00 to 59 for this reason.

Would like some left padding of the numbers with spaces to keep the width consistent. For example, instead of

-10 C
-1 C
0 C
1 C
9 C
10 C

do

-10 C
 -1 C
  0 C
  1 C
  9 C
 10 C

You may say, the temperature doesn't change that much throughout a normal day and you don't want to waste space in your panel all year long. That's true, but it can go from 9 to 10 to 9 several times in a day. Possibly a more complicated compromise would be to reduce the extra left padding space only when the extra space has been there for 3 degrees or 8 hours or more.