You have to adjust boiling point to elevation. I'm at 4500' on this side of the mountain, so the boiling points here is something like 104.4° (not exact, but close). You can use a potato or a block of wood to keep the probe off the grates. Hope this helps.
Question: What Temperature Does Water Boil?
At what temperature does water boil? What determines the boiling point of water? Here's the answer to this common question.
Answer: Short Answer: The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level).
Better Answer: The boiling point of water depends on the atmospheric pressure, which changes according to elevation. The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level), but water boils at a lower temperature as you gain altitude (e.g., on a mountain) and boils at a higher temperature if you increase atmospheric pressure (lived below sea level).