October Weather in Bethlehem Pennsylvania, United States
Daily high temperatures decrease by 11°F, from 70°F to 59°F, rarely falling below 48°F or exceeding 80°F.
Daily low temperatures decrease by 10°F, from 51°F to 41°F, rarely falling below 31°F or exceeding 62°F.
For reference, on July 21, the hottest day of the year, temperatures in Bethlehem typically range from 67°F to 85°F, while on January 30, the coldest day of the year, they range from 23°F to 37°F.
Average High and Low Temperature in October in Bethlehem
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on October. 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 October in Bethlehem
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 month of October in Bethlehem experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 37% to 42%.
The clearest day of the month is October 2, with clear, mostly clear, or partly cloudy conditions 63% of the time.
For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 56%, while on August 29, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 65%.
Cloud Cover Categories in October in Bethlehem
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Bethlehem, the chance of a wet day over the course of October is decreasing, starting the month at 28% and ending it at 23%.
For reference, the year's highest daily chance of a wet day is 39% on June 16, and its lowest chance is 21% on January 29.
Probability of Precipitation in October in Bethlehem
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 October in Bethlehem is decreasing, starting the month at 3.9 inches, when it rarely exceeds 7.2 inches or falls below 1.5 inches, and ending the month at 3.2 inches, when it rarely exceeds 5.4 inches or falls below 1.2 inches.
Average Monthly Rainfall in October in Bethlehem
Over the course of October in Bethlehem, 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, 17 minutes, implying an average daily decrease of 2 minutes, 34 seconds, and weekly decrease of 17 minutes, 58 seconds.
The shortest day of the month is October 31, with 10 hours, 29 minutes of daylight and the longest day is October 1, with 11 hours, 46 minutes of daylight.
Hours of Daylight and Twilight in October in Bethlehem
The earliest sunrise of the month in Bethlehem is 6:57 AM on October 1 and the latest sunrise is 33 minutes later at 7:30 AM on October 31.
The latest sunset is 6:43 PM on October 1 and the earliest sunset is 44 minutes earlier at 5:59 PM on October 31.
Daylight saving time is observed in Bethlehem during 2023, but it neither starts nor ends during October, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:30 AM and sets 15 hours, 5 minutes later, at 8:35 PM, while on December 22, the shortest day of the year, it rises at 7:22 AM and sets 9 hours, 16 minutes later, at 4:37 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in October in Bethlehem
The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.
Solar Elevation and Azimuth in October in Bethlehem
The figure below presents a compact representation of key lunar data for October 2023. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in October in Bethlehem
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 Bethlehem is decreasing during October, falling from 7% to 0% over the course of the month.
For reference, on July 29, the muggiest day of the year, there are muggy conditions 55% of the time, while on December 15, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in October in Bethlehem
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 Bethlehem is gradually increasing during October, increasing from 4.3 miles per hour to 4.9 miles per hour over the course of the month.
For reference, on February 26, the windiest day of the year, the daily average wind speed is 6.7 miles per hour, while on August 12, the calmest day of the year, the daily average wind speed is 3.5 miles per hour.
Average Wind Speed in October in Bethlehem
The hourly average wind direction in Bethlehem throughout October is predominantly from the west, with a peak proportion of 38% on October 30.
Wind Direction in October in Bethlehem
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 Bethlehem typically lasts for 6.5 months (198 days), from around April 9 to around October 24, rarely starting before March 24 or after April 25, and rarely ending before October 5 or after November 12.
During October in Bethlehem, the chance that a given day is within the growing season is very rapidly decreasing falling from 95% to 32% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in October in Bethlehem
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
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 Bethlehem are increasing during October, increasing by 196°F, from 3,197°F to 3,393°F, over the course of the month.
Growing Degree Days in October in Bethlehem
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 Bethlehem is decreasing during October, falling by 1.3 kWh, from 4.3 kWh to 3.0 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in October in Bethlehem
For the purposes of this report, the geographical coordinates of Bethlehem are 40.626 deg latitude, -75.370 deg longitude, and 354 ft elevation.
The topography within 2 miles of Bethlehem contains significant variations in elevation, with a maximum elevation change of 715 feet and an average elevation above sea level of 345 feet. Within 10 miles contains significant variations in elevation (906 feet). Within 50 miles contains very significant variations in elevation (2,264 feet).
The area within 2 miles of Bethlehem is covered by artificial surfaces (85%), within 10 miles by artificial surfaces (38%) and trees (31%), and within 50 miles by trees (56%) and cropland (22%).
This report illustrates the typical weather in Bethlehem, 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 Bethlehem.
For each station, the records are corrected for the elevation difference between that station and Bethlehem 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 Bethlehem is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Bethlehem and a given station.
The stations contributing to this reconstruction are:
To get a sense of how much these sources agree with each other, you can view a comparison of Bethlehem and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 data.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , 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 airports and weather stations are provided by AskGeo.com .
Maps are © OpenStreetMap contributors.
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.
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