Planning for the weather is a good way to make your trip to Isabela City relaxing and enjoyable, especially when you're splurging. The hottest months are usually April and May with an average temp of 81°F, while the coldest months are February and January with an average of 80°F. The rainiest months in Isabela City are June, July, August, and May, with each month seeing an average of 14 inches of rainfall.