Can the dew point be higher than the temperature?
Similarly, you may ask, can temperature be lower than dew point?
The dew point is always lower than (or equal to) the air temperature. If the air temperature cools to the dew point, or if the dew point rises to equal the air temperature, then dew, fog or clouds begin to form. No matter how hot the temperature gets, a dewpoint temperature of (say) 75 deg.
Similarly one may ask, how does the dew point affect the temperature?
The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%. The higher the dew point rises, the greater the amount of moisture in the air. This directly affects how "comfortable" it will feel outside.
It depends on the dry-bulb temperature, but typically the relative humidity will be between 90 and almost 100% (fog actually) in a really good rainstorm. As for dewpoint, depending on that temperature range, the dew point will be between one and eight degrees of the dry-bulb temperature.