Trying to make sense of figures stated as having 70% confidence

I have been asked to check a set of "predictions": I have been given a set of 30 numbers, being temperature predictions for the next 30 days. Each number has a stated confidence level, varying between 70% and 85%. I am not sure what a confidence level is in these circumstances. There is no other data supplied, such as sample size or how the figures were arrived at.
I was intending to compare these predicted values with actual values and adding error bars to allow for the confidence level, in order to see if the "predictions" had any value that was better than chance.
Is it possible to calculate an error range based on such a stated confidence level?
If so, how?
And is there a better way of comparing the predicted and actual figures to find if the prediction could be better than chance?

Thanks in advance for any help.