Unlike countries laying farther from the equator, Panama does not experience marked seasons based on changes in temperature, rather, Panama's seasons are divided into so called Wet and Dry Seasons. Around this time, strong north-easterly winds, known as the 'trade winds', begin to blow. Little or no rain may fall for many weeks in a row. May is often one of the wettest months, especially in the area of the Panama Canal, so the transition from the very dry conditions at the end of the Dry Season to the Wet Season can be very dramatic. With the coming of the rains, things cool down a little during the day and the trade winds disappear.
Some people like to think of the weather in the tropics as being the same thing year after year.
At least in Panama this in NOT true. However, there is also considerable variation in the amount of rain that falls between years. Very often, but not always, when there is a strong El Ni o in the Pacific, Panama experiences drier than normal conditions. 1997 and 1982 are examples of dry years associated with strong El Ni o events. Likewise, when the Pacific is experiencing La Ni a conditions, Panama tends to receive more rain than normal.