Satellite images come in two forms – visible satellite and infrared satellite. A visible satellite is simply an image taken from a satellite in Earth’s orbit. The infrared satellite image is based on temperature differences. The visible satellite is generally of more use to light aircraft pilots, but they are limited to use in daylight and will show areas of black during sunrise and sunset.
However, both visible and infrared satellite images are of little use to a pilot on their own. They can be used to see the big picture movement of weather systems over time, the location of fronts and an overview of cloud cover. However, be aware that smaller weather phenomena are difficult to see and low level weather can be obscured by layers of higher level cloud.
Weather radar images are created by a network of radar installations across the country which measure the location & intensity of precipitation (rain and rain-bearing clouds), and they are the only way of measuring this in real time. The radar data is displayed in a colour coded format.
Be sure to pay attention to the time of any weather radar images as those available online will typically be at least 15 minutes old. Weather can move a surprising distance in that time and there have been pilots who made a quick check of the weather radar on their phone or tablet before start-up, only to find the weather they were trying to avoid has moved overhead the airport by the time they reach the runway!