Calculating temperature correction is in both the NEC and CEC. Here's the CEC version:

64-202 Voltage of solar photovoltaic systems (see Appendix B)

1) The maximum photovoltaic source and output circuit voltage shall be the rated open-circuit voltage of the photovoltaic power source multiplied by 125%.

2) Notwithstanding Subrule 1), the maximum photovoltaic source and output circuit voltage shall be permitted to be calculated using a) the rated open-circuit voltage of the photovoltaic power source; b) the difference between 25 °C and the lowest expected daily minimum temperature; and c) the voltage temperature coefficient as specified by the manufacturer.