<p>Against the backdrop of global warming, the role of climate comfort in relation to the tourism industry has attracted growing attention. Focusing on the five provinces of Northwest China, this study constructs a monthly climate comfort index from data for 51 meteorological stations during 2010–2023 and aggregates it at the provincial level. The analysis identifies interannual trends using the Mann–Kendall test and Theil–Sen slope, depicts intra-annual seasonality, and uses Inverse Distance Weighting (IDW) interpolation to produce continuous spatial distribution maps, while testing spatial autocorrelation with Global Moran’s I and Local Indicators of Spatial Association (LISA). On the tourism side, Grey Relational Analysis (GRA) is employed to evaluate the contemporaneous proximity between the climate comfort index and provincial tourist arrivals, and robustness is examined by including versus excluding the pandemic years 2020–2022. The results show that: (i) from 2010 to 2023 the climate comfort of Northwest China increased overall but with notable interannual fluctuations. The intra-annual rhythm was characterised by a rise from late spring to early autumn, a relatively high and stable summer platform, and a marked decline in winter. Spatially, there was no significant global clustering, while local hot and cold spots appeared and shifted slightly over time. (ii) Climate comfort and tourist arrivals exhibited at least a moderate contemporaneous association, and the strength of this association varied across provinces. (iii) In some provinces (e.g. Qinghai and Ningxia), interannual variations in climate comfort were more closely aligned with fluctuations in tourist arrivals than were changes in economic indicators, tourism supply and transport accessibility, indicating that keeping seasonal conditions favourable and reducing climatic volatility can help support regional tourism planning and management.</p>