My son, 18 months, had his first seasonal seizure? What do I need to do from this day on..

It depends. A doctor will need to evaluate your son to determine the exact etiology of his seizure, and rule out long-term neurological problems. Children whose seizures are from high fevers are not at increased risk for more seizures or neurological problems later on, but seizures may put your child at risk. The doctor will also determine if your child needs medication to control his seizures.
Not worry so much! I have never heard the term "seasonal" seizure-do you mean "febrile" seizure- a seizure caused by fever?. Although scary to witness, they are common in children between 6 months and 4 years old-4% will have one. If the seizure is not prolonged (over 20 minutes) , your child is developing normally, and there is no family history of seizures, this should not develop into epilepsy.
??seasonal seizure?? Childhood is marked by a developing vulnerable nervous system.The system may respond to sudden rise in temperature with a febrile seizure, (1/20 kids) half of which never do it again.If this describes what happened, a normal exam after an initial event might not lead to much testing.Reguardless, your dr should give u guidelines for safety & when to take in for eval. Ask questions & be ready.
Seasonal vs Febrile. Do you mean febrile seizure? What needs to be done is at the first indication of illness, practice fever control,. Speak to your pediatrician about the proper dose of acetaminophen and ibuprofen, to be started even before fever begins. If necessary learn about sponging your child down with luke warm water, not cold, which would cause shivering and increase core temperature.