The blue circles show all the regions where your ads are being targeted. If you zoom into the map, you will see a small percentage sign within each blue circle. This will show you if your bids are being increased, decreased, or unchanged for each location.
The red ‘no entry’ circles represent all the areas where your ads are not being shown, because your weather targeting rules are not being met in those regions.
For a Facebook ad set, the green circles with ticks represent the regions where your ads are being shown, whilst the red no entry signs indicate areas where your ads are currently being paused (not being shown).