29-01-2025
Rainfall is officially measured at Phoenix Sky Harbor Airport. Why? Here's what to know
Phoenix Sky Harbor Airport is the official measure of weather in the city. Any records, rainfall or temperatures, depend on what happens at the airport.
It rained at Phoenix Sky Harbor International Airport on Wednesday, officially ending the city's second-longest dry streak on record.
Even though other areas saw rain at times throughout the dry streak, it didn't count because it wasn't at the airport. Why is that?
Meteorologist Isaac Smith with the National Weather Service in Phoenix said it is typical for weather measuring stations to be located at airports because weather data is essential for aviation operations.
Here's what Phoenix residents need to know about Sky Harbor's official weather gauges and sensors.
The official measuring station hasn't always been at the airport.
Starting in 1895 when records were first kept, the official temperature was recorded in the city's downtown. It wasn't until 1954 that meteorologists began making observations at the airport.
"Determining the wind speeds, wind directions, visibility and other factors, data, play into aviation," he said. "That's why we have this weather station at Sky Harbor."
The airport's observing station is a joint effort between the weather services, the Federal Aviation Administration, and the U.S. Department of Defense. The station includes sensors to measure wind speeds, dew point, air temperature, present weather, precipitation type and amount, visibility, cloud height and station pressure.
The instruments have been moved a couple of times as the airport expanded. They have been in their current location near the southern edge of the airport since 2000, Smith said.
More: How much rain did metro Phoenix get? See rainfall totals, weather radar and forecast
The Weather Service strives for consistency not only at a particular location but within its network of stations throughout the country. As a result, there are standards for positioning instruments such as thermometers and rain gauges.
Temperature sensors are placed in shade or, most often, in an enclosed structure that blocks sunlight but allows air to circulate. Placing the thermometer in direct sunlight could affect measurements. The enclosure also protects the thermometer from rain or snow.
The instruments are automated, transmitting data to their corresponding NWS office. (The Phoenix office is actually in Tempe, not at the airport.) Considering their importance to aviation, there are backup instruments at another location on the airport grounds.
Phoenix Sky Harbor International Airport is the official rain recording station for the Phoenix metro area, but have you wondered why those readings showed more or less than your home rain gauge received?
According to Rainlog, a rainfall monitoring network for Arizona, 'precipitation amounts are highly variable across Arizona due to topography and seasonal weather patterns. This is especially true during the monsoon when thunderstorms can produce heavy rainfall that is very localized.'
Zack Guido, a climate scientist and director of an international research program at the University of Arizona, said that winter storms are generally more predictable and widespread than Arizona's monsoon-powered summer storms.
'In the winter, we tend to get these frontal storms that have a larger footprint, and so there is a little bit more consistency in rainfall amounts,' Guido said. 'There's just an inherent variability in a storm itself that's going to produce variability spatially in rainfall, both in amount and intensity. The closer you are to the center of the storm's activity, the higher totals of precipitation you'll get.'
Arizona's monsoon season is an entirely different beast. What drives the rainfall in the summer months are convective storms — small, brief, typically weak storms that grow and die within an hour or so, according to the National Severe Storms Laboratory.
'These storms are quite localized where you could have half an inch or an inch of rain and quite literally a half mile away, no rain fell because that cell didn't pass over that area,' Guido said.
Former Arizona Republic reporters Weldon B. Johnson and Caralin Nunes contributed to this article.
This article originally appeared on Arizona Republic: Why is rainfall officially measured at Phoenix Sky Harbor Airport?
