If you plan to visit San Juan in September, the weather is typically alright, with an average high temperature of +88°F during the day and approximately 1 sunny days. Expect some rainy, though, as there are typically 20 rainy days in the month and around 148 mm of precipitation. The weather is changeable so you may have to pack for every eventuality. Search flightsin one click on Avionero.
Good to know:
September is usually the hottest month of the year in San Juan;
Average weather
☀️
+88°F
Avg. max. temperature
+73°F
Min.
+95°F
Max.
148 mm
Total precipitation
78%
Avg. humidity
2 m/s
Avg. wind
1 ☀️
Sunny Days
2 ⛅️
Cloudy
20 🌦
Rainy
Our opinion: San Juan has OK weather in September.
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Average temperature in San Juan in September
Here are the expected maximum, average and minimum temperatures in San Juan for September based on the historical data.
Last Year
Historical Data
Going from a maximum of +95°F during the day to a minimum of +75°F during the night, the temperature in September averages around +90°F.
The average maximum temperature goes down 9% by the end of the month, compared with the beginning of the month, from +90°F to +88°F.
Is San Juan warm or cold in September?
San Juan is typically hot in September.
Maximum temperatures go up compared to the previous month from +88°F to +88°F. The minimum temperature also goes up from +79°F to +79°F.
Make sure that you pack your summer linen and swimming costumes; it’s probably going to be hot.
September is the hottest month in San Juan, here is the comparison with other months:
Water temperature in San Juan in September
Water in San Juan in September is Very warm. It varies from +83°F to +86°F, with an average of +85°F.This is almost similar to the air temperature, which averages +88°F.
The water temperature in September is one of the warmest of the entire year:
The warmest water temperatures in San Juan are reached in September, when the average sea temperature rises to +85°F. The coldest water temperatures are in February, with an average of +79°F.
Can you swim in San Juan in September?
You can definitely swim in San Juan in September, the water is very warm (+85°F in average), and might even be unpleasant for ones who like it more fresh.
🦭
Cold
Below +61°F
🏄♂️
Fresh
61°F - 70°F
🏊
Comfortable
70°F - 77°F
👙
Warm
77°F - 82°F
🔥
Very warm
+82°C and up
Don't forget sunscreen and a hat, it's going to be hot!
Climate in San Juan in September
San Juan weather looks like this, on average, in September and the surrounding months.
August
September
October
Avg. temperature
+88°F
+88°F
+86°F
Min. temperature
+73°F
+73°F
+73°F
Max. temperature
+95°F
+95°F
+97°F
Rainfall
106 mm
148 mm
151 mm
Wind
3 m/s
2 m/s
2 m/s
Avg. water temperature
+84°F
+85°F
+84°F
Humidity
78%
78%
78%
Air pressure
1015 HPa
1013 HPa
1012 HPa
Sunny days
1
1
1
Cloudy days
3
2
3
Rainy days
22
20
21
Snowy days
0
0
0
September weather is still as ok as in August.The temperature levels stay the same in the area of +88°F for average maximum temperature during the day.Prepare for more rain. Average rainfall goes from 106 mm to 148 mm.Humidity levels don’t change as the month goes on, averaging around 78%.Winds are calmer in comparison to August, going down from 3 m/s to 2 m/s on average.The amount of sunny days stay about the same, averaging 1 sunny days during the month.
October brings much the same weather, it remains ok.
Wind speed in San Juan in September based on historical data.
Last Year
Historical Data
The average wind speed is 3 m/s getting up to 4 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in San Juan is gradually increasing during September, going from 4 m/s to 4 m/s over the course of the month.
Rain
Amount of rainfall in mm during September in San Juan based on historical data.
Last Year
Historical Data
Typically, there is a 77% chance of rain on an average day in September, with total rainfall of approximately 129 mm. The maximum amount of rainfall per day is around 19 mm, which is considered light rain.September is a pretty wet month with over 23 rainy days, so don’t forget to pack an umbrella, raincoat, and a pair of wellies.
September is one of the rainiest months in San Juan, here is a comparison with other months, total mm:
San Juan wettest month is October, where a typical day has a 68% chance of precipitation and 151 mm of rainfall per day. January, on the other hand, is the driest month with a mere 68% chance of precipitation and 38 mm of rainfall per day.
How was the weather last September in San Juan?
This is the weather in San Juan in September 2023:
1 September
🌫️
+89°F
2 September
☁️
+94°F
3 September
☀️
+91°F
4 September
☀️
+92°F
5 September
🌫️
+93°F
6 September
☀️
+90°F
7 September
☁️
+88°F
8 September
☁️
+89°F
9 September
🌧️
+90°F
10 September
☁️
+89°F
11 September
☁️
+90°F
12 September
☁️
+93°F
13 September
☁️
+95°F
14 September
☀️
+95°F
15 September
☀️
+91°F
16 September
☀️
+90°F
17 September
☁️
+90°F
18 September
☁️
+90°F
19 September
☁️
+91°F
20 September
☁️
+89°F
21 September
☁️
+88°F
22 September
☁️
+89°F
23 September
☀️
+89°F
24 September
☀️
+93°F
25 September
☁️
+90°F
26 September
☁️
+90°F
27 September
☁️
+88°F
28 September
☁️
+90°F
29 September
☁️
+91°F
30 September
🌧️
+89°F
In September 2023 San Juan had 8 sunny days, 18 cloudy days, and 2 rainy days. The average maximum temperature was +90°F, with an absolute maximum of +95°F and a minimum of +88°F. The average humidity was 82%, with a maximum of 100% and a minimum of 56%. The average wind speed was 3 m/s, with a maximum of 9 m/s and a minimum of 0 m/s.
Are you planning a trip in September?
Climate Change Over the Years
This is how San Juan climate has changed over the last 43 years.
The climate in San Juan in September has not changed that much over the last 43 years.
The average temperature was the lowest in 2008 (+84°F) and the highest in 2013 (+87°F). The driest year was 1994 with only 675 mm of rainfall, and the wettest year was 2023 with 2338 mm.
FAQ
Frequently asked questions about the weather in San Juan in September:
Is September a good time to visit San Juan?
It’s always a good time to visit San Juan, but the weather is changeable in September, so plan a mix of indoor and outdoor activities and exploring, and pack for every eventuality.
Can you sunbathe in San Juan in September?
Absolutely, September is hot in San Juan. Plan on beach and pool time, and ensure that you pack light and breathable options to stay comfortable.
Can you swim in San Juan in September?
Yes, you can swim in San Juan in September, the water is very warm, with temperature averaging at +85°F, but it's important to manage hydration and sun exposure.
Is San Juan rainy in September?
San Juan is often rainy in September. You may get a bit damp when outside, so pack an umbrella, and maybe even a raincoat.
Is it sunny in San Juan in September?
Usually, it’s not very sunny in San Juan in September, often it’s pretty cloudy. Pack for any eventuality; layering can help reduce the number of bulky items needed.
For this page, we’ve looked at the typical weather in San Juan, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.
