## 1 Introduction  
Assessing and mitigating human-driven impacts on climate is nowadays a well-established societal concern, as well as a highly pressing challenge for a number of actors operating across different scales and sectors. Interest from the scientific community in climate change dates back to more than a century ago [1]. However, it was only over the last few decades that the growing participation of public and non-public institutions to international summits on climate has provided a clear proof of the increasing importance attributed to this phenomenon from both the economic and the civil society [2, 3]. This has raised attention on a number of climate-related issues, recognized as priorities by the international community. Among them, the increasing trend in urbanization has been identified as a landmark for climate change. Today, cities host 55% of the world's population and this number is projected to rise to 68% by 2050 [4]. Cities generate more than 80% of global Gross Domestic Product (GDP), but they also consume about 2/3 of the world's energy and account for more than 70% of global greenhouse gas emissions [5]. Cities are also recognized as one of the most vulnerable places in terms of the future effects of climate change such as increased water shortages, negative health effects from Urban Heat Islands (UHI), and increased risk of flooding, among others [6]. This challenge is explicitly addressed by the United Nations (UN) Sustainable Development Goals (SDGs), in particular SDG 11 \"Make cities inclusive, safe, resilient and sustainable\" [7]. Nevertheless, the cities themselves can play a pivotal role in addressing climate change, since the way they are planned and governed may generate profound impacts on the minimization of emissions while also sustaining high living standards currently threatened by climate change [8]. This represents a unique opportunity for the academic and scientific community. Climate change adaptation and mitigation strategies must certainly start from collecting, understanding, and extracting knowledge from the multitude of geo-data sources available for cities [9]. Such sources can be roughly classified into space sensors and in-situ sensors. The former category includes optical and radar imagery, captured by satellites orbiting the Earth, as well as their derived products. An increasing number of Earth Observation (EO) initiatives around the globe is providing free and open access to such datasets with an unprecedented coverage and resolution. The most comprehensive example is the Copernicus Programme, which is empowering the European Commission with remotely-sensed information for land, marine, and atmospheric monitoring, emergency mapping, and climate change analysis [10]. The second category includes instead the burgeoning and non-stop amount of information generated by physical sensors, e.g., environmental sensor networks, and Internet of Things (IoT) devices and applications. These are complemented by, and often intersected with, crowdsourced geographic information collected by citizens [11]. This information can be contributed passively, e.g., from social networks, or actively within so-called Volunteered Geographic Information (VGI) projects, the most popular of which is OpenStreetMap [12], or Citizen Science (CS) initiatives. In urban contexts, many CS projects were accomplished to collect measurements of air temperature, air pollution, urban noise, etc. [13; 14; 15]. With this background, the present work contributes to the investigation of urban climate at the local scale through an approach based on the combination of space and in situ observations, the latter including crowdsourced geographic information. More in detail, the objective of the study is to analyze the effect of urban land cover on one of the most relevant climate-related variables, i.e., air temperature. This aims to provide insights into the study of urban heating issues, which are typically linked to anthropogenic factors such as Urban Heat Islands (UHIs) [16].