This report describes the typical weather at the Phoenix Sky Harbor International Airport (Phoenix, Arizona, United States) weather station over the course of an average July 4. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Phoenix, Arizona has a hot desert climate. The area within 25 mi of this station is covered by shrublands (85%), croplands (5%), forests (4%), built-up areas (3%), and grasslands (2%).
The temperature typically varies from 83°F to 106°F and is rarely below 77°F or above 111°F.
The coolest hours of the day are from 2am to 8am with the coldest at 6am, at which time the temperature is below 87°F three days out of four.
The warmest hours of the day are from noon to 8pm with the hottest at 4pm, at which time the temperature is above 103°F three days out of four.
The day has gained half its heat by 10am and lost it again by 11pm.
On July 4 the Sun rises at 5:23am and sets at 7:41pm.
Solar noon is at 12:32pm.
For reference, on the longest day of the year the Sun rises at 5:18am and sets at 7:40pm, while on the shortest day of the year it rises at 7:28am and sets at 5:24pm.
Astronomical twilight begins and ends 102 minutes before sunrise and after sunset at 3:41am and 9:22pm, respectively.
Nautical twilight begins and ends 63 minutes before sunrise and after sunset at 4:19am and 8:44pm, respectively.
Civil twilight begins and ends 28 minutes before sunrise and after sunset at 4:54am and 8:09pm, respectively.
Solar twilight begins and ends 36 minutes after sunrise and before sunset at 6:00am and 7:05pm, respectively.
The median cloud cover is 31% (mostly clear) and does not vary substantially over the course of the day.
On average, the sky is clear or mostly clear 51% of the time, partly cloudy 20% of the time, and mostly cloudy or overcast 22% of the time.
There is a 19% chance that precipitation will be observed at some point during the day.
The average measured liquid-equivalent quantity of precipitation is 0.014". Among only those days for which there is at least some measured precipitation, the average is 0.139" and the total rarely exceeds 0.259".
When precipitation does occur it is most often in the form of thunderstorms (64% of days with precipitation have at worst thunderstorms), slight rain (28%), and moderate rain (7%).
Precipitation is most likely around 11pm and least likely around noon.
Either snow is exceptionally unlikely to fall at this location on July 4 or this station does not reliably report precipitation types.
The relative humidity typically ranges from 17% (dry) to 35% (comfortable), rarely dropping below 9% (very dry), or exceeding 50% (mildly humid).
The air is driest at 4pm, at which time the relative humidity is less than 20% (dry) three days out of four; it is most humid at 5am, exceeding 26% (dry) three days out of four.
The dew point ranges from 46°F to 51°F with an average of 49°F.
For reference, comfortable indoor conditions should have a relative humidity between 30% and 50% with a dew point of less than 65°F.
Sustained wind speeds typically vary from 5 mph to 11 mph (light breeze to gentle breeze) over the course of the day.
The peak sustained wind speed typically occurs around 7pm and is rarely outside the range 6 mph to 16 mph (light breeze to moderate breeze).
The wind is most calm around 4am, rarely exceeding 9 mph (gentle breeze).
The wind is most often out of the west (27% of the time), east (20% of the time), and south east (11% of the time). The wind is least often out of the north east (4% of the time) and north (4% of the time).