nomadseason

September Weather in Santiago, Costa Rica

Last updated: August 23, 2025

In September, the average temperature in Santiago, Costa Rica is a pleasant 21°C (71°F). Throughout the month, temperatures can dip to a minimum of 17°C (63°F) and peak at a comfortable 27°C (81°F). Be prepared for ample rainfall, as the region experiences approximately 853 mm (33.6 in) of precipitation over 30 days, accompanied by an average humidity level of 81%.

September Temperature in Santiago

In September in Santiago, the average temperature is 21°C (71°F). Maximums can reach 27°C (81°F), while minimums can dip to as low as 17°C (63°F). This pleasant weather makes it an ideal time for traveling, whether you're looking to explore the outdoors or relax in the mild climate.

September Weather in Santiago: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Santiago, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Santiago, September typically has an average temperature of 21°C (71°F), with highs reaching up to 27°C (81°F) and lows dropping to around 17°C (63°F).
JanFebMarAprMayJunJulAugSepOctNovDec707172727272717171707070
Data source: Temperature data for Santiago generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Santiago

In Santiago in September, the total precipitation amount is 853 mm (33.6 in) over the course of 30 days.

September Precipitation Trends in Santiago

The chart displays monthly precipitation patterns in Santiago, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Santiago, September typically receives around 853 mm (33.6 inches) of precipitation spread over approximately 30 days.
JanFebMarAprMayJunJulAugSepOctNovDec1166574253706651683762853873503253
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Santiago

In Santiago in September, humidity is 81%. With an average temperature of 21°C (71°F), this humidity feels like a warm, enveloping blanket that makes traveling feel both refreshing and slightly heavy, often leading to a sticky sensation that can quickly deplete your energy.

September Average Humidity in Santiago

This chart illustrates the average monthly humidity levels in Santiago, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Santiago is approximately 81%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec68%68%66%67%69%84%85%82%81%80%80%73%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Santiago

In Santiago in September, the maximum UV index reaches 13, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's crucial to take protective measures. For detailed information, you can check the Hourly UV Index in Santiago.

Maximum UV Index Levels in Santiago for September

The chart shows the monthly maximum UV Index (UVI) for Santiago in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Santiago typically reaches 13, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec111314141514141313131110
Data source: Santiago September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Santiago Compares to Other Months

Weather in Santiago varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Santiago, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Santiago, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather21°C (71°F)116 mm (4.6 inches)68%extreme
February Weather22°C (71°F)65 mm (2.5 inches)68%extreme
March Weather22°C (72°F)74 mm (2.9 inches)66%extreme
April Weather22°C (72°F)253 mm (10.0 inches)67%extreme
May Weather22°C (72°F)706 mm (27.8 inches)69%extreme
June Weather22°C (72°F)651 mm (25.6 inches)84%extreme
July Weather22°C (72°F)682 mm (26.9 inches)85%extreme
August Weather22°C (71°F)762 mm (30.0 inches)82%extreme
September Weather21°C (71°F)853 mm (33.6 inches)81%extreme
October Weather21°C (70°F)873 mm (34.4 inches)80%extreme
November Weather21°C (71°F)503 mm (19.8 inches)80%extreme
December Weather21°C (71°F)253 mm (10.0 inches)72%very high

Compare Santiago's Climate with Cities Worldwide