Fortaleza is a hot city, with little variation in temperature across the year; this happens because Fortaleza is located very near the Equatorial Line. There is a slight decrease from April to August, but the temperature remains between 25.5 and 27.5 degrees Celsius.
There is a clear concentration of rain in the first half of the year. From August to December, Fortaleza sees very little rain.
With no defined season, Fortaleza just has the raining season from January to July and the arid one from August to December.
Remember that in the austral hemisphere seasons are inverted compared to the USA and Europe (Spring: September through November - Summer: December through February - Fall: March through May - Winter: June through August).