Prague awakens in Spring, when rising temperatures make it a great time to visit.
This is a great season if you wish avoid the oppressive heat of summer and see the wonderful blossoms on the fruit trees of Petřín Hill, wander in the royal palace gardens or visit the leafy grounds of Vysehrad. There are not so many tourists around so you don’t have to worry about crowds on the Charles Bridge, and hotel prices are more reasonable etc. The beginning of spring might be a bit chilly with occasional snow showers as winter hangs on, but from mid- April and May temperatures get higher (ranging from 16 to 25°C).
Consider bringing a jacket or warm raincoat, gloves in March, umbrella, hat and sunglasses. You can also buy a cheap umbrella while you’re arrive.