People come here for the beaches and the Honolulu weather that's nice all year round. So what exactly should you expect? Oahu has a tropical climate so expect warm and humid, some breezes and winds and don't be surprised if it rains.
Warm and Humid
Most of the time there are some nice breezes coming through that keep it comfortable even with the humidity. When there's no breeze, however, it can get uncomfortable. Luckily you can just hop in the ocean for a swim to cool off.
Winds
We get Kona Winds from the southeast in the winter and Trade Winds from the northeast most of the year. Most of the time we have gentle breezes that feel wonderful and keep things cool. There are times, however, when the winds are so strong it's difficult to walk around outside!
Rain
Other parts of the island of Oahu get heavy rains but Honolulu gets much less. Most of the time when it does rain, it's short and light and stays warm while it's raining. People continue to walk around in shorts and flip flops, maybe an umbrella, but the light rains do not bother most people. Every once in a while, Honolulu does get a few days of steady rain. It's still warm but without an umbrella, you're going to get soaked.
Earthquakes
In October 2006, there was a major earthquake on the island of Hawaii. Oahu felt it and was even out of power for the day. Earthquakes are not common in Hawaii. Volcano activity, yes, but usually not major earthquakes.