Source: www.weather-and-climate.com
As shown from the weather charts above, the best months to climb Mt Kinabalu would be around Feb-Apr periods. These are the months with the lowest average rainfall and highest hours of sunshine over the entire year.
If the weather conditions are very poor, the park may refuse to allow hikers to proceed with attempts to summit to Low's Peak. So it is advisable to do proper research and study in advance.