It is not unusual for an iPad to become warm when being used - more so when using some types of iPad case and when charging. High screen brightness and/or CPU intensive Apps will also create more heat.
High ambient temperatures will also impact natural cooling. Being summer in the Northern Hemisphere, higher temperatures might be expected. If applicable, try charging your iPad in a cooler location - and certainly away from direct sunlight.
The key point is that whilst your iPad may become very warm in normal use, the iPad should not become uncomfortably hot to handle. If your iPad is becoming too hot to hold, you should take your iPad along to the Genius Bar at your local Apple Store - where the technicians can examine and test your iPad for faults.
Genius Bar Reservation and Apple Support Options - Apple