In summary, I analyzed the dataset from one low-cost weather unit and compared it with forecasting, reanalysis and observational data. The low-cost unit measured temperature with ±1.3°C from 5 types of sensors. The comparison of the data from this unit and the forecasting data indicated that in building, the temperature is higher than one forecast about 3.4°C. The forcasting data is on average higher than the reanalysis 1.1°C in 2019. Finally, the observational data from Lang station is higher than the MERRA-2's about 2°C. One implication of this analysis is that there is no source data could represent the temperature for Hanoi. Any analysis should be specified the dataset used and pronounced limitations.