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  5. September

Average Weather in September in Trebbio Italy

Daily high temperatures decrease by 8°F, from 72°F to 64°F, rarely falling below 57°F or exceeding 80°F.

Daily low temperatures decrease by 7°F, from 58°F to 51°F, rarely falling below 44°F or exceeding 63°F.

For reference, on July 26, the hottest day of the year, temperatures in Trebbio typically range from 62°F to 77°F, while on January 12, the coldest day of the year, they range from 26°F to 37°F.

Average High and Low Temperature in September

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in September

Average Hourly Temperature in September in Trebbio1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM4 AM8 AM12 PM4 PM8 PM12 AMAugOctcoldcoolcomfortablecomfortablewarmvery cold
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Marlinton, West Virginia, United States (4,430 miles away) and Rockport, Massachusetts, United States (3,847 miles) are the far-away foreign places with temperatures most similar to Trebbio (view comparison).


The month of September in Trebbio experiences rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 35% to 47%.

The clearest day of the month is September 1, with clear, mostly clear, or partly cloudy conditions 65% of the time.

For reference, on May 2, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 55%, while on July 21, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 73%.

Cloud Cover Categories in September

Cloud Cover Categories in September in Trebbio181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 165%Sep 165%Sep 3053%Sep 3053%Sep 1162%Sep 1162%Sep 2158%Sep 2158%clearmostly clearpartly cloudymostly cloudyovercast
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.


A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Trebbio, the chance of a wet day over the course of September is essentially constant, remaining around 25% throughout.

For reference, the year's highest daily chance of a wet day is 35% on June 3, and its lowest chance is 15% on January 30.

Probability of Precipitation in September

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).


To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during September in Trebbio is gradually increasing, starting the month at 2.8 inches, when it rarely exceeds 4.6 inches or falls below 0.9 inches, and ending the month at 3.3 inches, when it rarely exceeds 6.2 inches or falls below 0.7 inches.

Average Monthly Rainfall in September

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.


Over the course of September in Trebbio, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 32 minutes, implying an average daily decrease of 3 minutes, 10 seconds, and weekly decrease of 22 minutes, 9 seconds.

The shortest day of the month is September 30, with 11 hours, 46 minutes of daylight and the longest day is September 1, with 13 hours, 18 minutes of daylight.

Hours of Daylight and Twilight in September

Hours of Daylight and Twilight in September in Trebbio181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrAugOctSep 2312 hr, 11 minSep 2312 hr, 11 minnightnightdaydaySep 113 hr, 18 minSep 113 hr, 18 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Trebbio is 6:38 AM on September 1 and the latest sunrise is 36 minutes later at 7:14 AM on September 30.

The latest sunset is 7:56 PM on September 1 and the earliest sunset is 56 minutes earlier at 7:00 PM on September 30.

Daylight saving time is observed in Trebbio during 2018, but it neither starts nor ends during September, so the entire month is in daylight saving time.

For reference, on June 21, the longest day of the year, the Sun rises at 5:28 AM and sets 15 hours, 43 minutes later, at 9:11 PM, while on December 21, the shortest day of the year, it rises at 7:55 AM and sets 8 hours, 41 minutes later, at 4:36 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in September

The solar day over the course of September. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.


We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Trebbio is gradually decreasing during September, falling from 2% to 0% over the course of the month.

For reference, on July 28, the muggiest day of the year, there are muggy conditions 9% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in September

Humidity Comfort Levels in September in Trebbio181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%10%20%30%40%50%60%70%80%90%100%AugOctSep 12%Sep 12%Sep 300%Sep 300%Sep 111%Sep 111%Sep 210%Sep 210%humidhumidcomfortablecomfortabledrydrymuggymuggy
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.


This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Trebbio is essentially constant during September, remaining around 4.2 miles per hour throughout.

For reference, on April 6, the windiest day of the year, the daily average wind speed is 4.9 miles per hour, while on December 18, the calmest day of the year, the daily average wind speed is 3.9 miles per hour.

The highest daily average wind speed during September is 4.2 miles per hour on September 29.

Average Wind Speed in September

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
The hourly average wind direction in Trebbio throughout September is predominantly from the east, with a peak proportion of 37% on September 30.

Wind Direction in September

Wind Direction in September in TrebbioSE181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctsoutheastnorthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Trebbio typically lasts for 7.3 months (223 days), from around April 2 to around November 11, rarely starting before March 10 or after April 24, and rarely ending before October 23 or after November 30.

The month of September in Trebbio is reliably fully within the growing season.

Time Spent in Various Temperature Bands and the Growing Season in September

Time Spent in Various Temperature Bands and the Growing Season in September in Trebbiogrowing season181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOct100%Sep 16100%Sep 1690%Oct 2390%Oct 23very coldcoldcoolcomfortablewarm
The percentage of time spent in various temperature bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Trebbio are increasing during September, increasing by 328°F, from 1,958°F to 2,286°F, over the course of the month.

Growing Degree Days in September

The average growing degree days accumulated over the course of September, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Trebbio is decreasing during September, falling by 1.5 kWh, from 5.2 kWh to 3.7 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in September

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.


For the purposes of this report, the geographical coordinates of Trebbio are 45.713 deg latitude, 10.461 deg longitude, and 2,221 ft elevation.

The topography within 2 miles of Trebbio contains large variations in elevation, with a maximum elevation change of 2,533 feet and an average elevation above sea level of 2,287 feet. Within 10 miles contains large variations in elevation (6,663 feet). Within 50 miles also contains extreme variations in elevation (12,126 feet).

The area within 2 miles of Trebbio is covered by trees (83%) and grassland (10%), within 10 miles by trees (75%), and within 50 miles by cropland (37%) and trees (37%).

Data Sources

This report illustrates the typical weather in Trebbio year round, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There are 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Trebbio.

For each station, the records are corrected for the elevation difference between that station and Trebbio according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

The estimated value at Trebbio is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Trebbio and a given station.

The stations contributing to this reconstruction are: Verona Brescia Airport (35%, 33 kilometers, south); Verona Villafranca Airport (27%, 49 kilometers, southeast); Il Caravaggio International Airport (29%, 59 kilometers, west); and Paganella (meteorological station) (9%, 66 kilometers, northeast).

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.


The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.