Average high temperature and rainfall in San Juan in December. © Scott S. Bateman

San Juan weather in December is almost worth the risk. It is midway between the end of the rainy season and the beginning of the dry season.

The Caribbean hurricane season makes San Juan a risky place to visit between August and November when the average rainfall is five to six inches a month. The threat of hurricanes or tropical storms is higher than normal.

Cruise visitors flock to the capital of Puerto Rico anyway during hurricane season because of its great historical attractions such as Old San Juan. It also is a convenient stopping point for cruises to the eastern and southern Caribbean.

Cruise visitors who stay only for an afternoon in December don’t face much risk for rain. But hotel visitors who stay a week or more face a higher risk. For both, the risk gets better in December than any time from August through November.

December Rainfall

While August through November average five to six inches of rain per month, December averages about four, according to the U.S. National Weather Service. It’s an improvement over the previous months, but it’s not as good as the two to three inches a month from January through March.

Visitors should assume that the risk of rain is lower in the second half of December than the first half as Puerto Rico transitions from the rainy season to the dry season.

Unfortunately, the number of days that it rains in December is about the same as the four previous months. Each month has an average of 14 days of rain or about every other day on average.

By comparison, January has about 13 days and February through April average about eight to nine days.

San Juan Temperatures in December

December weather in San Juan is often warm enough for land activities but a bit cool at times for the water.

The average daytime temperature in San Juan during December is 83 degrees Fahrenheit or about 28 Celsius, according to the U.S. National Weather Service. The average nighttime temperature is 72 degrees Fahrenheit or 23 Celsius.

Water temperatures hover between the nighttime lows and daytime highs. But cool northern currents plus a wind chill factor sometimes makes the water feel a bit chilly for swimming, especially in the early mornings.

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