Proposing practical solutions to mitigate the effects of climate change on the electricity system requires thorough understanding and quantification. This paper introduces a new method of quantifying dynamic network capacity at the transmission level, using established thermal models and a set of regional expansion plan tools. The results suggest this approach can increase component capacity by up to 21% during winter and up to 16% during nighttime hours for overhead lines. This approach offers a viable option for electricity operators to address the challenge of balancing the need to reduce failure rates and capacity loss with the crucial demand for new investment in transmission assets, reducing more than 1% of system cost expansion by 2050.