We have an excellent collection of worksheets for Year 4 Statistics including tally charts, pictograms and bar charts and we have just published a tricky set on interpreting bar charts using negative numbers. This is not an explicit target for Year 4 although bar charts and negative numbers are separate targets, but this type of question has come up in the SATs with a Year 4 reference (S41).
Concentrating on temperatures in various cities around the world, the worksheets are excellent practice at working with negative numbers in a real-life context. For example: finding the difference in temperature between Oslo (3 degrees C) and Boston (-6 degrees C).
The bar charts themselves provide an excellent visual interpretation of the temperatures, much in the same way as bar modelling does as mentioned above.