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🇵🇷 Weather in San Juan in September
This is what the weather in San Juan (Puerto Rico) was like in September over the years 2017–2026.
Key facts at a glance
Prevailing weather: Light rain
Avg. daytime high
30.9 °C
29.7 °C – 31.8 °C
Avg. night-time low
27.1 °C
26.5 °C – 27.8 °C
Avg. rain days in period
27.2
91 % of days · ≥ 1.0 mm
Avg. precipitation in period
165 mm
77.0 mm – 389 mm
Avg. cloud cover
71 %
This data source has no sunshine hours – average cloud cover is shown instead.
Avg. sea temperature
29.8 °C
Sea temperature available for 2 of 10 years.
Extremes: Highest temperature 33.0 °C (13 Sep 2023) · Lowest temperature 25.1 °C (30 Sep 2017) · Avg. daily peak wind 19 km/h
Weather mix of all days
- 19Partly cloudy
- 6Cloudy
- 177Light rain
- 95Rain
Summary
- On average 30.9 °C during the day and 27.1 °C at night.
- On average 27.2 rain days (Rain day = at least 1.0 mm of precipitation) with 165 mm of precipitation in total.
- The sea averaged 29.8 °C.
- Prevailing weather: Light rain.
- Warmest year: 2026 (avg. 31.8 °C), coolest: 2017 (avg. 29.7 °C).
- Wettest year: 2017 (389 mm), driest: 2023 (77.0 mm).
- Extremes: 33.0 °C on 13 Sep 2023 and 25.1 °C on 30 Sep 2017.
Overall values from all 10 years. How is this calculated?
Charts
Temperatures per year
Average over your travel period
Avg. daytime high: 2017 30°, 2018 31°, 2019 31°, 2020 31°, 2021 30°, 2022 30°, 2023 32°, 2024 31°, 2025 31°, 2026 32°. Avg. night-time low: 2017 27°, 2018 26°, 2019 27°, 2020 27°, 2021 27°, 2022 27°, 2023 28°, 2024 28°, 2025 27°, 2026 27°. Sea temperature: 2017 –, 2018 –, 2019 –, 2020 –, 2021 –, 2022 –, 2023 –, 2024 –, 2025 30°, 2026 30°.
Precipitation & rain days
Precipitation (mm): 2017 389, 2018 99, 2019 166, 2020 93, 2021 221, 2022 261, 2023 77, 2024 114, 2025 134, 2026 96.
Year by year
2026
Avg. max31.8°Avg. min27.4°- Rain days
- 27 Rain days
- Precipitation
- 95.8 mm
- Avg. cloud cover
- –
- Sea temperature
- 29.6 °C
Max 32.8 °C · Min 26.5 °C
2025
Avg. max31.4°Avg. min27.1°- Rain days
- 25 Rain days
- Precipitation
- 134 mm
- Avg. cloud cover
- 71 % cloudy
- Sea temperature
- 29.9 °C
Max 32.5 °C · Min 25.8 °C
2024
Avg. max31.3°Avg. min27.7°- Rain days
- 28 Rain days
- Precipitation
- 114 mm
- Avg. cloud cover
- 64 % cloudy
- Sea temperature
- –
Max 32.8 °C · Min 26.6 °C
2023
Avg. max31.7°Avg. min27.8°- Rain days
- 27 Rain days
- Precipitation
- 77.0 mm
- Avg. cloud cover
- 68 % cloudy
- Sea temperature
- –
Max 33.0 °C · Min 26.8 °C
2022
Avg. max30.3°Avg. min26.9°- Rain days
- 29 Rain days
- Precipitation
- 261 mm
- Avg. cloud cover
- 73 % cloudy
- Sea temperature
- –
Max 31.8 °C · Min 25.7 °C
2021
Avg. max30.4°Avg. min27.0°- Rain days
- 29 Rain days
- Precipitation
- 221 mm
- Avg. cloud cover
- 65 % cloudy
- Sea temperature
- –
Max 31.8 °C · Min 26.3 °C
2020
Avg. max31.0°Avg. min27.1°- Rain days
- 26 Rain days
- Precipitation
- 93.5 mm
- Avg. cloud cover
- 66 % cloudy
- Sea temperature
- –
Max 32.5 °C · Min 26.7 °C
2019
Avg. max31.3°Avg. min27.0°- Rain days
- 27 Rain days
- Precipitation
- 166 mm
- Avg. cloud cover
- 78 % cloudy
- Sea temperature
- –
Max 32.4 °C · Min 26.3 °C
2018
Avg. max30.6°Avg. min26.5°- Rain days
- 25 Rain days
- Precipitation
- 99.5 mm
- Avg. cloud cover
- 69 % cloudy
- Sea temperature
- –
Max 31.7 °C · Min 25.9 °C
2017
Avg. max29.7°Avg. min26.6°- Rain days
- 29 Rain days
- Precipitation
- 389 mm
- Avg. cloud cover
- 81 % cloudy
- Sea temperature
- –
Max 31.4 °C · Min 25.1 °C
Frequently asked questions
- How warm is it in San Juan in September?
- Daytime highs averaged 30.9 °C, night-time lows 27.1 °C. The highest value of the past 10 years was 33.0 °C (13 Sep 2023), the lowest 25.1 °C (30 Sep 2017).
- How often does it rain in San Juan in September?
- On average there were 27.2 rain days (at least 1 mm) with 165 mm of precipitation in total.
- How warm is the sea in San Juan in September?
- The sea temperature averaged 29.8 °C (open-sea point approx. 3 km from the town).
Check your exact travel dates
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Other destinations in September
Data sources
- Weather data
- Data obtained from the NASA Langley Research Center (LaRC) POWER Project funded through the NASA Earth Science/Applied Science Program
Reanalysis (weather model constrained by observations) on a coarse grid of about 50 km. Values represent a large area and can differ from local conditions, especially on islands, coasts and in mountains. Snow depth is the model value for the grid cell, not the depth on the slopes. No sunshine duration.
Reanalysis (weather model constrained by observations)
Reanalysis values represent a grid cell (approx. 25–50 km) and may differ from local measurements on coasts, islands and in mountains. - Sea temperature
- MUR SST data were provided by JPL under support by NASA MEaSUREs program; accessed via NOAA CoastWatch ERDDAP
Daily multi-scale ultra-high resolution (≈ 1 km) analysis of satellite measurements (infrared, microwave) and in-situ data. Represents the foundation temperature below the daily warm surface layer. (Satellite and in-situ analysis) - Sea measuring point approx. 3 km from the location (18.500, -66.100)
- Place search
- Natural Earth (public domain) · GeoNames (CC BY 4.0) / OpenStreetMap (ODbL)