The National Weather Service is probably one of the best sources for this. They have lots of maps for both current conditions and forecast conditions. You can find their page for graphical forecast maps here:
For example, here is what their graphical forecast looks like for temperatures at 5 PM EDT today:
The same page also has forecast maps for:
- Dew Point
- QPF (Quantitative Precipitation Forecast, the amount of rain/snow/sleet, measured in equivalent rainfall.)
- Wind Speed and Direction
- Wind Gusts
- Sky Cover
- Snow Amounts
- Ice accumulation
- Relative Humidity
- Apparent Temperature (i.e. heat index or wind chill, as appropriate.)
- Wave Height
They also have a 'metric units' link you can click that displays a page showing you how the colors map to the appropriate metric unit scale, if you prefer Celcius, for example.
Weather Underground is also a good source. You can find their interactive temperature map here, though they're a private company so it would probably violate the copyright to post the image here. The data is freely available on their website, though.