From Alderman Carl Franco:

Due to the frigid temps, the side streets were not plowed curb to curb. If that were done the city would have wanted to salt those streets but the low temps would not allow the salt to be effective and hence create a more slippery situation.
With the snow event tonight, the plan is to plow the side streets curb to curb tomorrow once the snow stops and salt then as the temps will be high enough for the salt to be effective. We have used a lot of salt thus far this year and resources are slim so we don’t want to waste salt when it won’t have an effect.