Last updated: February 24, 2025
September in Grand Isle, United States, showcases a warm coastal climate with maximum temperatures reaching 32°C (91°F) and an average of 27°C (81°F), providing ideal beach weather for visitors. However, with an average minimum temperature of 21°C (70°F), evenings offer a mild respite. The month is characterized by 166 mm (6.5 in) of rainfall over approximately 15 days, contributing to the region’s lush landscapes. With humidity levels lingering around 79%, the air carries a noticeable tropical feel, making it a vibrant yet occasionally wet experience for all who come to enjoy the beauty of Grand Isle.
In September, Grand Isle enjoys a delightful transition as the summer's warmth lingers, reflected in the temperatures that range from a mild 21°C (70°F) at night to a sun-drenched 32°C (91°F) during the day, with an average of 27°C (81°F). This makes it one of the warmest months of the year, continuing the trend set by the hotter months of July and August. As the heat begins to soften in October, locals and visitors alike savor the last vestiges of summer, indulging in outdoor activities under sunny skies before the cooler fall temperatures take hold. The steady increase in warmth from the earlier months culminates in September’s balmy embrace, making it an ideal time to experience the vibrant beauty of Grand Isle.
In September, Grand Isle experiences a significant decline in precipitation compared to the summer months, with 166 mm (6.5 in) recorded over 15 rainy days. This drop follows the peak rainfall of August, which saw 298 mm (11.7 in) across 23 days, highlighting a seasonal shift as the region transitions from the wettest part of the year. The September showers provide a refreshing respite while still contributing to the overall summer total, reinforcing the trend of late-season rain that supports local ecosystems. As autumn approaches, this moderation in precipitation may signal the onset of drier months ahead, particularly in contrast to the heavy downpours of July and August.
In September, Grand Isle experiences a slight uptick in humidity, averaging around 79%. This marks a gradual return from the summer's driest months in June, July, and August, where humidity dipped to 74% and 73% respectively. The humidity in September paves the way for a more comfortable early fall, as it hovers near the consistent levels of 81% seen at the start of the year. As the months transition, the humidity begins to rise again towards winter, highlighting a seasonal rhythm where the air retains moisture, particularly noticeable in the colder months of November and December, when humidity peaks at 81% and 84%. Overall, September's humidity serves as a bridge between summer and fall, inviting a refreshing change while still echoing the lingering warmth of summer.
As summer transitions into fall, September in Grand Isle continues to showcase a healthy dose of sunshine with an UV Index of 11, maintaining its status in the extreme exposure category. This marks a slight dip from the peak levels of July and August, yet sun seekers should stay vigilant as the burn time remains a quick 10 minutes. This trend of elevated UV levels throughout the warmer months underscores the importance of protecting your skin during outdoor activities. With the UV Index noticeably easing into October, where it drops to 9, individuals are encouraged to enjoy the lingering summer warmth while prioritizing sun safety. For detailed UV index information, visit Grand Isle UV Index.
UV Risk Categories
As summer transitions into fall, September in Grand Isle offers a delightful blend of warmth and sunshine, boasting 281 hours of golden rays. This month showcases a gentle decline in daylight compared to the bustling peak of May, where residents basked in a vibrant 334 hours. However, September still holds its charm, maintaining a generous amount of sunlight akin to the lively months preceding it. With October just around the corner, which brings a slight increase to 291 hours, Grand Isle revels in a comfortable balance, perfect for outdoor activities as the summer heat begins to fade. The overall trend reveals a beautiful legacy of sunshine that characterizes the region, allowing both locals and visitors to enjoy the best of this coastal paradise as it eases into the autumn season.
In Grand Isle, the likelihood of sunny weather in September is around 43%, which is a notable increase compared to the summer months when sunshine chances drop to their lowest at 27% in July. As the summer heat wanes, the chance for clearer skies returns, bringing a refreshing transition into early fall. This trend is mirrored in October, where the probability of sunny weather rises back to 51%, suggesting that while September might not be the sunniest month, it serves as a promising lead-up to sunnier days ahead. Overall, September offers a sweet spot for those wanting to enjoy milder temperatures with a fair chance of sunshine before the more consistent sunny spells of autumn set in.
As September unfolds in Grand Isle, the length of daylight begins to shift, with the sun gracing the sky for 12 hours each day. This marks a subtle transition from the summer months of June through August, when residents enjoyed the fullest days of up to 13 hours. The early fall brings a slight decrease in daylight, setting the stage for the cooler months ahead. It's a time that blends the lingering warmth of summer with the promise of autumn, as daylight gradually decreases, dipping to 11 hours in October and then to 10 hours by November. This gradual decline highlights the rhythm of nature, allowing inhabitants to relish the remaining sunlit hours while anticipating the shorter days of winter.
As summer wanes and September rolls into Grand Isle, the average wind speed gently rises to 4.9 m/s (11 mph), a slight increase from August's 4.8 m/s (11 mph). This subtle uptick marks a shift as the breezier days of early fall begin to breeze in, following a notably calmer summer, particularly in July, where winds dipped to 3.8 m/s (9 mph). The trend indicates a gradual return to more consistent winds, reminiscent of the spring months, making September a transitional time when the warmth of summer still lingers, yet whispers of autumn begin to unfold. This balance invites outdoor enthusiasts to enjoy the milder weather with refreshing sea breezes, setting the stage for more dynamic conditions as the year progresses.
The weather in Grand Isle 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 Grand Isle and find detailed weather information for every month.
September and January present stark contrasts in weather patterns. In September, temperatures are significantly warmer, ranging from a minimum of 21°C (70°F) to a maximum of 32°C (91°F), with an average of 27°C (81°F). This month also sees considerable rainfall, totaling 166 mm (6.5 in) over 15 days, and maintains a high humidity level of 79%. Conversely, January experiences much cooler temperatures, with a range from 0°C (33°F) to 24°C (76°F) and an average of 15°C (59°F). Rainfall is less frequent, with only 100 mm (3.9 in) over 8 days, while humidity remains relatively constant at 81%. For more details on January weather, visit Grand Isle weather in January.
September and February present contrasting weather patterns. September exhibits warm temperatures, with a minimum of 21°C (70°F) and an average of 27°C (81°F), peaking at a high of 32°C (91°F). This month is also characterized by frequent rainfall, accumulating 166 mm (6.5 in) over 15 days, while humidity hovers around 79%. In stark contrast, February experiences cooler temperatures with a minimum of 0°C (32°F) and an average of 17°C (62°F), reaching a maximum of 24°C (76°F). Precipitation is lower in February at 95 mm (3.8 in) over 12 days, and the humidity remains similar at 81%. For a detailed look at February conditions, explore Grand Isle weather in February.
In September, the weather is characterized by warmer temperatures, with a minimum of 21°C (70°F) and an average of 27°C (81°F), reaching a maximum of 32°C (91°F). This month also sees significant precipitation, totaling 166 mm (6.5 in) over about 15 days, contributing to a high humidity level of 79%. In contrast, March experiences much cooler conditions, with temperatures ranging from a low of 6°C (43°F) to an average of 19°C (66°F) and a maximum of 26°C (78°F). Additionally, rainfall is less frequent in March, amounting to 65 mm (2.6 in) over roughly 8 days, while maintaining the same humidity level of 79%. For more details about the weather in March, you can visit Grand Isle weather in March.
In comparing the weather of September and April, it's clear that September is notably warmer, with average temperatures ranging from a minimum of 21°C (70°F) to a maximum of 32°C (91°F). In contrast, April has cooler temperatures, averaging between 12°C (54°F) and 26°C (79°F). Additionally, September experiences significantly more rainfall, totaling 166 mm (6.5 in) over 15 days, compared to April's 106 mm (4.2 in) over just 9 days. Despite this, both months maintain high humidity levels, hovering around 79% in September and slightly higher at 81% in April. For a more detailed look at April's weather, you can visit Grand Isle weather in April.
September and May present distinct weather characteristics, with September tending to be warmer and wetter. In September, temperatures range from a minimum of 21°C (70°F) to a maximum of 32°C (91°F), averaging around 27°C (81°F). The month also experiences significant rainfall, with about 166 mm (6.5 in) spread over 15 days and a humidity level of 79%. In contrast, May features milder temperatures, with a minimum of 17°C (63°F) and a maximum of 29°C (85°F), averaging 25°C (77°F). May sees less precipitation at 99 mm (3.9 in) over 10 days and slightly lower humidity at 77%. For more detailed insights, you can check Grand Isle weather in May.
In comparing the weather between September and June, we find that September experiences slightly lower temperatures, with a minimum of 21°C (70°F) and a maximum of 32°C (91°F), in contrast to June's warmer temperatures, which range from a minimum of 24°C (75°F) to a maximum of 31°C (87°F). Both months have an average temperature of 27°C (81°F), but September tends to be more humid, with humidity levels at 79% compared to June's 74%. Precipitation is also slightly higher in June, totaling 195 mm (7.7 in) over 15 days, compared to September's 166 mm (6.5 in) over the same number of days. For more detailed information on June weather, you can visit Grand Isle weather in June.
When comparing the weather in September to July, several notable differences emerge. In September, the temperatures range from a minimum of 21°C (70°F) to a maximum of 32°C (91°F), with an average of 27°C (81°F). This period also experiences significant rainfall, with a total precipitation of 166 mm (6.5 inches) over about 15 days and higher humidity levels averaging 79%. In contrast, July sees slightly warmer temperatures, with a minimum of 25°C (77°F) and an average of 28°C (83°F), peaking at the same maximum of 32°C (90°F). Precipitation is higher in July, totaling 232 mm (9.2 inches) across 19 days, though humidity is more moderate at 74%. For a detailed look at July's weather, you can visit Grand Isle weather in July.
In comparing the weather between August and September, there are some notable differences. September generally experiences slightly cooler temperatures, with a minimum of 21°C (70°F) and an average of 27°C (81°F), compared to August's minimum of 25°C (77°F) and average of 28°C (83°F). Despite this, September sees more frequent rainfall, with 166 mm (6.5 in) of precipitation over 15 days, while August records a significantly higher total of 298 mm (11.7 in) across 23 days. Additionally, humidity remains relatively high in both months, but it's slightly greater in September at 79%, compared to August's 73%. For a more detailed look at the weather conditions, you can check Grand Isle weather in August.
In comparing the weather between September and October, we see a notable drop in temperatures. September boasts a minimum of 21°C (70°F) and averages around 27°C (81°F), with maximums reaching 32°C (91°F). In contrast, October experiences cooler temperatures, with a minimum of 12°C (54°F) and an average of 25°C (77°F), peaking at 29°C (84°F). Precipitation also decreases slightly from September’s 166 mm (6.5 in) over 15 days to October’s 128 mm (5.0 in) across 13 days, with humidity remaining relatively stable at 79% in September and 77% in October. For more detailed weather insights, you can check Grand Isle weather in October.
In September, temperatures are significantly warmer, with a minimum of 21°C (70°F) and an average high of 32°C (91°F), making it one of the hottest months of the year. The month also experiences considerable rainfall, averaging 166 mm (6.5 in) over 15 days, coupled with high humidity levels around 79%. In contrast, November brings a notable drop in temperatures, with a minimum of 7°C (45°F) and an average high of 26°C (79°F). Precipitation decreases as well, with only 56 mm (2.2 in) expected over just 6 days, while humidity remains relatively high at 81%. For more detailed information, you can check Grand Isle weather in November.
In September, the weather is warm and humid, with average temperatures ranging from a minimum of 21°C (70°F) to a maximum of 32°C (91°F) and significant rainfall of 166 mm over about 15 days. This high humidity of 79% contributes to a sultry atmosphere, making it a typical late summer month.
In contrast, December brings a much cooler and drier climate, featuring average temperatures between 6°C (43°F) and 24°C (75°F). Although precipitation is lower at 109 mm over 10 days, the humidity rises slightly to 84%. This change from the warmth of September to the briskness of December can be quite pronounced, reflecting the shift from summer to winter. For more details on what to expect, visit Grand Isle weather in December.
As September arrives in Grand Isle, the weather starts to transition, offering a blend of warm days and increased humidity. This month sets itself apart with a notable rise in precipitation, often resulting in brief but intense showers across approximately half the month. While the average temperature remains comfortable, the peak highs hint at the summer's lingering warmth, presenting a unique mix of cozy beach days and moody, rain-soaked afternoons. This period serves as a gentle reminder of the impending shift to autumn, making it a unique time to experience the island's charm. For a deeper dive into Grand Isle's weather patterns, explore Grand Isle Climate.