September Weather in Merthyr Mawr, United Kingdom

Last updated: March 17, 2025

September in Merthyr Mawr, United Kingdom presents a blend of mild warmth and occasional rain, making it a unique time of year. Temperatures can soar to a pleasant 27°C (80°F), with an average of 15°C (59°F), while nighttime lows dip to a refreshing 5°C (41°F). This month sees about 92 mm (3.6 in) of precipitation over 12 days, contributing to the lush greenery in the region. With a humidity level averaging 79%, visitors can expect a somewhat damp but invigorating atmosphere, perfect for exploring the scenic landscapes that Merthyr Mawr has to offer.

September Temperature in Merthyr Mawr

As September unfolds in Merthyr Mawr, temperatures start to shift from the warmth of summer to the cooler embrace of autumn. The month begins with a mild minimum of 5°C (41°F), gradually transitioning to an average of 15°C (59°F), and peaking at a comfortable 27°C (80°F), reminiscent of late summer days. This gentle decline in temperature marks a notable trend as the region moves from the highs of August, where peaks reached 28°C (82°F), indicating that while the days are still pleasantly warm, a crispness in the air hints at the impending fall. Overall, September offers a delightful balance, inviting residents and visitors alike to relish the lingering warmth before the cooler months settle in.

September Weather in Merthyr Mawr: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Merthyr Mawr, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec434345495459636258544845
Data source: Temperature data for Merthyr Mawr generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Merthyr Mawr

In September, Merthyr Mawr experiences a notable transition in its climate, showcasing an average precipitation of 92 mm (3.6 in) over approximately 12 days. This marks a slight decrease from the preceding months, with August having recorded a higher total of 106 mm (4.2 in) across 16 days. September serves as a bridge into the wetter autumn season, as it prepares to usher in heavier rainfall in October, which peaks at 146 mm (5.7 in). This month’s consistent precipitation indicates a shift toward more frequent rainy days, paving the way for the lush landscapes that define the region during this time of year. Overall, the data illustrates a gradual increase in rainfall as the year progresses, highlighting the characteristic wetness of the British climate.

September Precipitation Trends in Merthyr Mawr

The chart displays monthly precipitation patterns in Merthyr Mawr, 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.
JanFebMarAprMayJunJulAugSepOctNovDec831111015780858610693146111144
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Merthyr Mawr

In September, Merthyr Mawr experiences a humidity level of 79%, marking a slight increase from the drier summer months of July and August, which recorded 70% and 73% respectively. As the seasons transition, the return of moisture in the air is evident, hinting at the forthcoming autumn months. This uptick in humidity lays the groundwork for the wetter conditions that typically characterize the later part of the year, with humidity levels rising to 89% by October and peaking at 90% in November. Observing this progression, it’s clear that September acts as a bridge between the summer's relative dryness and the lush, damp atmosphere of autumn in the UK.

September Average Humidity in Merthyr Mawr

This chart illustrates the average monthly humidity levels in Merthyr Mawr, with September's data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, allowing you to see how September's humidity levels compare to other months.
JanFebMarAprMayJunJulAugSepOctNovDec89%88%86%84%80%80%70%73%79%89%90%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Merthyr Mawr

In September, Merthyr Mawr experiences a UV Index of 6, placing it in the high exposure category with a burn time of just 25 minutes. This marks a slight decrease from the summer months, where the index peaked at 8, indicating a transition towards milder conditions as autumn approaches. However, the UV levels remain significant enough to necessitate sun protection, especially during midday hours. As the days shorten and temperatures cool, it’s essential to remain mindful of sun safety while enjoying the beautiful September days in this picturesque area. For more insights on UV exposure trends, visit Merthyr Mawr UV Index.

Maximum UV Index Levels in Merthyr Mawr for September

The chart shows the monthly maximum UV Index (UVI) for Merthyr Mawr 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.
JanFebMarAprMayJunJulAugSepOctNovDec124678876421
Data source: Merthyr Mawr 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.

September Sunshine in Merthyr Mawr

As September unfolds in Merthyr Mawr, the charm of early autumn is accompanied by a generous 296 hours of sunshine. This delightful month offers a gentle transition from the sun-drenched days of summer, where July peaks at a stunning 410 hours. Although September's sunlight diminishes compared to its predecessors, it still shines brighter than the bleak winter months, which average a mere 128 hours in November and 104 hours in December. This steady decline from summer bliss to winter's chill indicates a seasonal ebb, yet September remains a vibrant time to revel in the lingering warmth before the colder days set in, inviting both locals and visitors to embrace the beauty of change.

Monthly Sunshine Duration in Merthyr Mawr: September Highlighted

The September sunshine duration represents the total number of hours Merthyr Mawr experiences direct sunlight during the month of September, excluding cloudy or obstructed periods. This chart compares the sunshine duration of September with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec87h142h205h320h393h373h410h362h296h233h128h104h
Data source: Merthyr Mawr September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Merthyr Mawr During September

In Merthyr Mawr, September sees a 28% chance of sunny weather, maintaining a consistent but modest likelihood of sunshine as the summer months draw to a close. While this figure is slightly below the bustling months of April (54%) and July (41%), it reflects a gradual decline from the vibrant sunshine experienced in the peak of summer. With the chances dipping in October to 21%, September remains a transitional month, hinting at the approaching autumn while still offering a reasonable opportunity for those seeking to enjoy the outdoors before the clouds roll in. So, whether you're planning a leisurely stroll or an outdoor gathering, September holds the promise of occasional sunny breaks to savor the last days of warmth.

Percentage of Sunny Days in September in Merthyr Mawr

The chart illustrates the percentage of sunny days in Merthyr Mawr throughout the year, with September highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Merthyr Mawr experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec22%23%30%54%33%27%41%32%28%21%30%20%
Data source: Merthyr Mawr September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Merthyr Mawr in September

In September, Merthyr Mawr transitions from the long, sun-soaked days of summer to the crispness of autumn, offering about 12 hours of daylight. This reduction marks a noticeable shift from the peak of 16 hours in June and July, and although it feels shorter, September still boasts more daylight than the months ahead. As nature begins its slow descent into winter, the dwindling daylight hints at the changing seasons while providing a beautiful backdrop for the vibrant fall foliage. The pattern reveals a gentle decline from the summer peak, setting the stage for the shorter days of October and November, where sunlight fades to just 10 and 8 hours, respectively.

Average Daylight Hours in Merthyr Mawr for September

The chart illustrates the variation in daylight duration in Merthyr Mawr throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h 23m9h 58m11h 55m13h 54m15h 39m16h 33m16h 4m14h 30m12h 35m10h 36m8h 49m7h 52m
Data source: Merthyr Mawr daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Merthyr Mawr

In Merthyr Mawr, as summer gradually gives way to autumn, September showcases a gentle whisper with an average wind speed of 3.8 m/s (9 mph). This marks a slight decline from the more spirited breezes of August, which saw an average of 4.4 m/s (10 mph). The diminishing winds in September reflect a broader trend of reduced breeziness as temperatures cool—this month typically enjoys milder gusts compared to the earlier months of the year, particularly April and June, when winds were notably softer at 3.9 m/s and 3.6 m/s, respectively. As we approach October, when winds pick up to about 5.1 m/s (11 mph), September serves as a serene transition, embodying the tranquil essence of early autumn in this picturesque region.

Average September Wind Speed in Merthyr Mawr

The chart displays monthly wind speed patterns in Merthyr Mawr, with values for each month shown alongside September's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how September's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec5.36.05.13.94.93.63.54.43.8 m/s5.14.45.7
Data source: Merthyr Mawr September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Merthyr Mawr Compares to Other Months

The weather in Merthyr Mawr changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of September's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in Merthyr Mawr and find detailed weather information for every month.

In September, the weather is generally milder, with average temperatures ranging from a minimum of 5°C (41°F) to a maximum of 27°C (80°F), and an average of 15°C (59°F). It is also characterized by higher humidity at 79% and more rainfall, totaling 92 mm (3.6 in) over 12 days. In contrast, January presents colder conditions, with temperatures ranging from a minimum of -3°C (28°F) to a maximum of 13°C (56°F), averaging at 6°C (43°F). Though it experiences slightly less precipitation at 83 mm (3.3 in) over the same number of days, the humidity rises to 88%. For a more detailed look at January weather, check out Merthyr Mawr weather in January.

In comparing the weather between September and February, notable contrasts emerge. September typically experiences milder temperatures, ranging from a minimum of 5°C (41°F) to a maximum of 27°C (80°F), while February's temperatures are much cooler, with a minimum of -3°C (26°F) and a maximum of 15°C (59°F). Precipitation is more frequent in February, with 111 mm (4.4 in) over 15 days, compared to September's 92 mm (3.6 in) over 12 days. Additionally, February tends to be more humid, with levels reaching 88% compared to September's 79%. For more specific details on February's weather, you can visit Merthyr Mawr weather in February.

When comparing the weather in September and March, it’s evident that September is generally milder with average temperatures ranging from 5°C to 27°C (41°F to 80°F), while March experiences cooler conditions, with temperatures ranging from -5°C to 18°C (23°F to 64°F). September boasts lower precipitation levels (92 mm over 12 days) compared to March's 101 mm over 17 days, indicating that March tends to be wetter despite its lower temperatures. Additionally, humidity is slightly higher in March at 86%, compared to September’s 79%. For more detailed information, you can check Merthyr Mawr weather in March.

September and April showcase distinct weather patterns, each with its own charm. In September, temperatures range from a minimum of 5°C (41°F) to a pleasant average of 15°C (59°F), peaking at 27°C (80°F). This month also experiences higher precipitation levels, with 92 mm (3.6 in) spread over 12 days and humidity at 79%. In contrast, April features cooler temperatures, starting at a minimum of -1°C (30°F) and averaging 9°C (49°F), with a maximum of 20°C (68°F). Precipitation is lighter at 56 mm (2.2 in) over 10 days, accompanied by slightly higher humidity at 84%. For more detailed information about the weather specifics in April, you can check Merthyr Mawr weather in April.

In comparing the weather between September and May, September tends to be warmer, with average temperatures reaching 15°C (59°F) compared to May's 12°C (54°F). While September boasts maximum temperatures of 27°C (80°F), May peaks at 24°C (75°F). Both months experience a similar number of rainy days, with September receiving slightly more precipitation at 92 mm (3.6 in) compared to May’s 80 mm (3.2 in). Humidity levels remain fairly consistent, with September at 79% and May at 80%. For a closer look at May's weather, you can visit Merthyr Mawr weather in May.

In comparing the weather patterns of September and June, both months showcase similar average temperatures, hovering around 15°C (59°F). However, September experiences a slightly broader temperature range, with a minimum of 5°C (41°F) and a maximum of 27°C (80°F), compared to June's minimum of 7°C (45°F) and maximum of 27°C (81°F). Additionally, September sees a bit more precipitation, totaling 92 mm (3.6 in) over 12 days, while June has 85 mm (3.3 in) over 13 days. Humidity levels are also quite close, with September at 79% and June at 80%. For more details on the weather during this period, you can check Merthyr Mawr weather in June.

In comparing the weather of September and July, we observe that September tends to be slightly cooler, with average temperatures ranging from a minimum of 5°C (41°F) to a maximum of 27°C (80°F), while July has a minimum of 9°C (48°F) and an average high of 27°C (81°F). Precipitation levels are close between the two months, with September seeing 92 mm (3.6 in) over 12 days and July experiencing 86 mm (3.4 in) across the same number of days. Moreover, September's humidity is higher at 79%, compared to July's 70%, contributing to a more humid feel as summer transitions into autumn. For a closer look at July's weather, you can explore Merthyr Mawr weather in July.

In comparing the weather between August and September, we can observe some notable differences. September experiences cooler temperatures, with a minimum of 5°C (41°F) compared to August's minimum of 9°C (48°F). The average temperature in September is around 15°C (59°F), slightly lower than August's average of 16°C (62°F). While the maximum temperatures are relatively similar, peaking at 27°C (80°F) in September and 28°C (82°F) in August, September sees more precipitation, totaling 92 mm (3.6 in) over 12 days, whereas August has 106 mm (4.2 in) over 16 days. Additionally, September is more humid, with a humidity level of 79% compared to August's 73%. For a closer look at the August weather in Merthyr Mawr, check out Merthyr Mawr weather in August.

September and October display notable differences in weather patterns, with September offering milder temperatures and less precipitation. In September, average temperatures range from a minimum of 5°C (41°F) to a maximum of 27°C (80°F) with 92 mm (3.6 in) of rain over 12 days. In contrast, October sees a drop in average temperatures, ranging from a chilly minimum of 1°C (33°F) to a maximum of 21°C (70°F), along with increased precipitation of 146 mm (5.7 in) spread across 17 days. Additionally, October tends to be more humid, with humidity levels rising to 89%. For more details, you can check the Merthyr Mawr weather in October.

September and November present a notable transition in weather. In September, temperatures range from a comfortable minimum of 5°C (41°F) to a pleasant maximum of 27°C (80°F), with an average of 15°C (59°F). The month experiences around 92 mm (3.6 in) of precipitation spread over 12 days, while humidity hovers at 79%. In contrast, November sees a significant drop in temperatures, with minimums dipping to -1°C (31°F) and an average of just 9°C (48°F). Although maximum temperatures remain relatively mild at 16°C (60°F), the month is wetter, receiving 111 mm (4.4 in) of rain over 16 days, and humidity rises to 90%. This stark change illustrates the shift from early fall warmth to late autumn chill. For more specific details, check out Merthyr Mawr weather in November.

In September, temperatures in Merthyr Mawr range from a minimum of 5°C (41°F) to a maximum of 27°C (80°F), with an average of 15°C (59°F). The month experiences 92 mm (3.6 in) of precipitation over 12 days, and humidity levels hover around 79%. In contrast, December brings much cooler temperatures, with averages dropping to 7°C (45°F) and highs of only 13°C (55°F). The minimum temperature can plummet to -2°C (29°F), accompanied by increased precipitation of 144 mm (5.7 in) over 18 days and a rise in humidity to 89%. For a detailed look at the December weather, visit Merthyr Mawr weather in December.

Compare Merthyr Mawr's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Merthyr Mawr

As September rolls in at Merthyr Mawr, the weather presents a delightful transition from the summer's heat to the more temperate embrace of autumn. With maximum temperatures still reaching a warm 27°C, the month offers a pleasant escape before the chill sets in, making it a great time for outdoor activities. However, it also ushers in increased rainfall, with 12 days of precipitation typical for this month, contributing to a humidity level of 79%. This shift in climate not only revitalizes the lush landscapes but also invites a more introspective experience in nature. Embrace the unique September charm by exploring what the season has to offer in this beautiful part of Wales by checking out the detailed insights on Merthyr Mawr Climate.