This quantitative study evaluates how 71 Spanish undergraduate students understand the uncertainty inherent to deterministic forecasts. Understanding is based on several questions that asked participants what they expect given a forecast presented under the deterministic paradigm for a specific lead time and a particular weather parameter. Students’ responses to the temperature forecast as it is usually presented in the media expect an uncertainty degree of ±1-2°C. Regarding wind speed, uncertainty shows a deviation of ±5-10 km/h, while the uncertainty range assigned to the precipitation amount shows a deviation of ±30 mm from the specific value provided in a deterministic format. Participants perceive the minimum night temperatures as the less biased parameter from the deterministic forecast, while the amount of rain is perceived as the most biased one. Additionally, participants were then asked about their probabilistic threshold for taking appropriate precautionary action under distinct decision-making scenarios of temperature, wind speed and rain. Results indicate that participants have different probabilistic thresholds for taking protective action and that context and presentation influence forecast use. Finally, participants were asked about the meaning of the probability of precipitation (PoP) forecast. Around 40% of responses reformulated the by default options while around 20% selected the correct answer, following previous studies related to this research topic. As a general result, it has been found that participants infer uncertainty into deterministic forecasts and they are mostly used to take action in the presence of decision-making scenarios. In contrast, more difficulties were found when interpreting probabilistic forecasts.