Moderate rainfall is ideal, especially if distributed just the right way: optimally there should be a dry season before, during, and after the harvest, followed by blossom showers, which soak the earth just enough to initiate simultaneous flowering of all the coffee plants. During this short interval of flowering, showers are undesirable as not to interfere with the setting of the coffee fruits. Once the coffee fruit are set, months of rain are welcomed to follow, more often in the afternoon after a sunny bright morning that helps the plants reach their ripeness. This weather pattern leads to evenly maturing fruit and makes for a far easier and more consistent harvest.

In reality almost none of the coffee-growing areas meet this climatic utopia. Typically, less than ideal rain distribution produces uneven ripening cherries makes the task of picking only ripe fruit far harder and more expensive to perform.  Kenya coffees grow in arid conditions, where Guatemala coffees receive heavy rains, even during the harvest period.

There are two optimal growing climates for growing Arabica coffees:

  1. Within the subtropical regions, at high altitudes between 1800-3600 feet with very well defined rainy and dry seasons. These conditions result in one coffee growing season and one maturation season, usually in the coldest part of autumn.
  2. Within the equatorial regions at altitudes between 3600-6300 feet. Frequent rainfall causes almost continuous flowering, which results in two coffee harvesting seasons. The period of highest rainfall determines the main harvesting period, while the period of least rainfall determines the second harvest season.

Robusta coffee is grown at much lower altitudes between sea level-3000 feet in an areas North and South of the equator.

There are numerous factors that play a critical role in the production and final cost of growing quality coffee ranging from cloud cover, position of the sun, temperature range, rainfall and its pattern of distribution, soil composition and structure, accessibility some of which the farmer grower can control and some which are nothing short of force major.

Higher altitudes can produce longer growing seasons and ideal temperatures, below 90 °F and above 45 °F year round, with high quotidian contrast, ideal for growing complex, floral, bright yet balanced coffees. But not without an expense: steep mountain slopes mean high maintenance and labor costs due to poor accessibility and proneness to soil erosion.