There is not much we can accurately predict 5 days into the future, so relatively speaking, the 5-day forecast comes a lot closer to doing that than most aspects of life. As for the 10-day forecast, it's likely that meteorologists know exactly how unpredictable the weather conditions 10 days in the future can be.
Likewise, what do meteorologists use to predict the weather?
Meteorologists use a variety of tools to help them gather information about weather and climate. Some more familiar ones are thermometers which measure air temperature, anemometers which gauge wind speeds, and barometers which provide information on air pressure.
How do we get the weather forecast?
Weather forecasts are made by collecting as much data as possible about the current state of the atmosphere (particularly the temperature, humidity and wind) and using understanding of atmospheric processes (through meteorology) to determine how the atmosphere evolves in the future.
What tool is used to predict the weather?
A barometer measures atmospheric pressure, a thermometer measures the temperature, and an anemometer measures wind speed and direction. Weather radar detects precipitation in the clouds, and the Doppler radar takes measurements of winds in clouds in order to predict severe storms and tornadoes.