Matza balls 'explode' at high altitude

The answer has more to do with pressure than temperature. The higher your altitude the lower the pressure. Because the water is at a lower pressure than at sea level there are fewer water molecules in a given water volume so the water does not place as much force on the surface of your Matza balls as they cook. That allows them to expand and explode. A pressure cooker would fix the problem or you could try to wrap them in mulsin or similar to simulate pressure. While this may sound silly (I won’t go into the science)you could also try making them bigger.

Some recipes for mazta have chemical leavening. Chemical leaveners operate very differently at varied elevations. See here for conversion and tips. This is a very common problem. Judging by the problem, it seems like you were previously closer to sea level and this recipe worked fine. Am I right?

Basically [no pun intended], baking powder is a mixture of desiccant, baking soda, and cream of tartar. When water mixes to make a solution, the chemical reaction ensues releasing CO2 gas as a byproduct of soda bicarbonate and cream of tartar (an acid).

Higher elevation causes this reaction to carry out much faster, and this is how your balls are blowing apart. The solution [no pun intended] is to make a stronger dough with more flour, more kneading, and more powder so that the rise is slower, more controlled, and better tolerated by the ball.

Heat also causes the reaction to take place faster. It may be annoying, but try pulling the soup off to cool for a bit, then bring it slowly back up to temperature.