FSI Insights No 34, July 2021. This paper discusses the challenges that emerge when trying to adapt traditional stress tests to banks' climate-related risks. These challenges relate to: (i) data availability and reliability; (ii) the adoption of very long time horizons; (iii) uncertainty around future pathways of key reference variables covering physical risks (eg floods, temperature increases and rising sea levels); and (iv) uncertainty relating to transition risks (eg changes in climate policies, technologies or consumer preferences).