Machine learning-based temperature mapping in Sydney: Accuracy, transferability, and scalability

Urban heat is a growing concern for public health, energy demand, and urban liveability. High-resolution air temperature (T a ) data are needed for developing effective, localised adaptation strategies, but obtaining such data at the city scale remains a challenge as weather stations are often sparse and unevenly distributed. To address this data gap, we developed a machine learning (ML) framework that creates high-resolution, gridded T a maps using crowdsourced observations and diverse geospatial datasets describing the city, and evaluated its accuracy, transferability, and performance under varying data availability conditions. This framework uses satellite-derived land surface temperature (LST), urban form and fabric datasets, and meteorological variables to train a convolutional neural network (CNN) model. The approach was implemented in Sydney, Australia, producing 30 m gridded T a estimates (at ~10:00 a.m. local time) with high accuracy on an independent held-out test set (R² = 0.97; RMSE = 0.91 °C), surpassing previously reported ML performance. We further assessed the generalisation and spatial transferability of this method, showing that the CNN model maintained strong predictive accuracy for unseen locations across the city (R² = 0.91–0.93; RMSE = 1.27–1.44 °C). Model performance also remained stable when the number of T a stations was significantly reduced by ~80%. Performance was more variable for unseen days (R² = 0.66–0.93; RMSE = 1.52–2.60 °C), indicating that ML-based T a mapping requires training data representative of diverse weather conditions. We find that high-resolution city-descriptive datasets are beneficial but not essential, as comparable accuracy was achieved using only globally available predictors. These results indicate that the proposed framework is transferable to other cities, including those in data-sparse regions. The study provides an effective and scalable approach for city-scale air temperature mapping, which is urgently needed for urban heat assessment, climate adaptation, and public health planning.