November is rainy; winter is cold and often bleak.
Many sights reduce their hours sharply or close altogether.
Prices are rock-bottom.
Holidaymakers have gone home; prices drop.
Spring is glorious everywhere, though it can be pretty wet in May/early June.
Autumn is particularly special in the hills (eg Bükk and Mátra); festivals mark the szüret (grape harvest).
Summer is warm, sunny and unusually long everywhere.
Resorts at Lake Balaton and in the northern Hungary hills book out; expect long queues at attractions and high prices everywhere.
Many cities grind to a halt in August, the 'cucumber-growing season' when nothing much else is happening.