Average Weather in May in Perth Australia
Daily high temperatures decrease by 6°F, from 73°F to 67°F, rarely falling below 62°F or exceeding 80°F.
Daily low temperatures decrease by 4°F, from 55°F to 51°F, rarely falling below 44°F or exceeding 62°F.
For reference, on February 11, the hottest day of the year, temperatures in Perth typically range from 65°F to 86°F, while on July 19, the coldest day of the year, they range from 48°F to 63°F.
Average High and Low Temperature in May
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on May. 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 May
The month of May in Perth experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 30% throughout the month.
The clearest day of the month is May 10, with clear, mostly clear, or partly cloudy conditions 70% of the time.
For reference, on April 23, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 31%, while on January 19, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 86%.
Cloud Cover Categories in May
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Perth, the chance of a wet day over the course of May is very rapidly increasing, starting the month at 18% and ending it at 34%.
For reference, the year's highest daily chance of a wet day is 42% on July 22, and its lowest chance is 3% on December 30.
Probability of Precipitation in May
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 May in Perth is rapidly increasing, starting the month at 1.9 inches, when it rarely exceeds 3.8 inches or falls below 0.5 inches, and ending the month at 3.9 inches, when it rarely exceeds 6.7 inches or falls below 1.5 inches.
Average Monthly Rainfall in May
Over the course of May in Perth, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 38 minutes, implying an average daily decrease of 1 minute, 17 seconds, and weekly decrease of 8 minutes, 57 seconds.
The shortest day of the month is May 31, with 10 hours, 13 minutes of daylight and the longest day is May 1, with 10 hours, 51 minutes of daylight.
Hours of Daylight and Twilight in May
The earliest sunrise of the month in Perth is 6:48 AM on May 1 and the latest sunrise is 20 minutes later at 7:07 AM on May 31.
The latest sunset is 5:38 PM on May 1 and the earliest sunset is 19 minutes earlier at 5:20 PM on May 31.
Daylight saving time is not observed in Perth during 2018.
For reference, on December 21, the longest day of the year, the Sun rises at 5:07 AM and sets 14 hours, 15 minutes later, at 7:21 PM, while on June 21, the shortest day of the year, it rises at 7:16 AM and sets 10 hours, 3 minutes later, at 5:20 PM.
Sunrise & Sunset with Twilight in May
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 Perth is essentially constant during May, remaining within 1% of 1% throughout.
For reference, on February 14, the muggiest day of the year, there are muggy conditions 8% of the time, while on August 14, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in May
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 Perth is gradually increasing during May, increasing from 11.5 miles per hour to 12.2 miles per hour over the course of the month.
For reference, on January 23, the windiest day of the year, the daily average wind speed is 14.2 miles per hour, while on May 2, the calmest day of the year, the daily average wind speed is 11.4 miles per hour.
The lowest daily average wind speed during May is 11.4 miles per hour on May 2.
Average Wind Speed in May
Wind Direction in May
Perth is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average surface water temperature in Perth is essentially constant during May, remaining within 1°F of 71°F throughout.
Average Water Temperature in May
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).
Temperatures in Perth are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in May
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 Perth are increasing during May, increasing by 324°F, from 4,777°F to 5,101°F, over the course of the month.
Growing Degree Days in May
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 Perth is gradually decreasing during May, falling by 1.0 kWh, from 3.9 kWh to 2.9 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in May
For the purposes of this report, the geographical coordinates of Perth are -31.952 deg latitude, 115.861 deg longitude, and 69 ft elevation.
The topography within 2 miles of Perth contains only modest variations in elevation, with a maximum elevation change of 325 feet and an average elevation above sea level of 66 feet. Within 10 miles also contains only modest variations in elevation (459 feet). Within 50 miles contains only modest variations in elevation (2,005 feet).
The area within 2 miles of Perth is covered by artificial surfaces (52%), sparse vegetation (19%), trees (14%), and water (13%), within 10 miles by artificial surfaces (51%) and trees (19%), and within 50 miles by water (37%) and trees (28%).
This report illustrates the typical weather in Perth 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 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Perth.
For each station, the records are corrected for the elevation difference between that station and Perth 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 Perth is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Perth and a given station.
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.