Weather in Guam in September 2025
Average weather
Average temperature in Guam in September
The temperature in September is +31°C on average, with a range between a maximum of +32°C during the day and a minimum of +24°C at night.
The average maximum temperature goes up 13% by the end of the month, compared with the beginning of the month, from +30°C to +31°C.
Is Guam warm or cold in September?
Guam is typically warm in September.
Maximum temperatures go up compared to the previous month from +29°C to +29°C. The minimum temperature also goes up from +26°C to +26°C.
It’s generally warm, but pack a long-sleeve shirt for evenings.
Take a look at how September is compared to other months in Guam:
Climate in Guam in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +29°C | +29°C | +29°C | ||||
| Min. temperature | ||||||
| +23°C | +23°C | +22°C | ||||
| Max. temperature | ||||||
| +33°C | +34°C | +33°C | ||||
| Rainfall | ||||||
| 457 mm | 403 mm | 385 mm | ||||
| Wind | ||||||
| 3 m/s | 2 m/s | 3 m/s | ||||
| Humidity | ||||||
| 84% | 84% | 84% | ||||
| Air pressure | ||||||
| 1008 HPa | 1008 HPa | 1008 HPa | ||||
| Sunny days | ||||||
| 0 | 0 | 0 | ||||
| Cloudy days | ||||||
| 0 | 0 | 1 | ||||
| Rainy days | ||||||
| 29 | 28 | 29 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September weather is still as ok as in August. The temperature levels stay the same in the area of +29°C for average maximum temperature during the day. As September arrives, the amount of rainfall goes down. On average, the rainfall volume decreases from 457 mm to 403 mm. Humidity levels don’t change as the month goes on, averaging around 84%. 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 0 sunny days during the month.
October brings much the same weather, it remains ok.
Wind
The average wind speed is 2 m/s getting up to 4 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in Guam is gradually decreasing during September, going from 4 m/s to 1 m/s over the course of the month.
Rain
How was the weather last September in Guam?
Climate Change over Years
The climate in Guam in September has not changed much over the last 43 years.
The average temperature was the lowest in 1983 (+27°C) and the highest in 2018 (+31°C). The driest year was 1983 with only 1154 mm of rainfall, and the wettest year was 2023 with 4623 mm.
FAQ
Is September a good time to visit Guam?
Can you sunbathe in Guam in September?
Is Guam rainy in September?
Is it sunny in Guam in September?
Monthly weather in Guam
Source of the data
For this page, we’ve looked at the typical weather in Guam, 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.
