When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Singapore City Airport is roughly less than Gander. You can assume this to be the case over the next 0 days.
You can imagine temperatures to be in the 33 °C range in April. The weather in Gander is generally colder than Singapore City Airport's. As flight availability is subject to become more limited as peak season approaches it is ideal to book in a timely manner.