Heat check: rising temperatures and health crises in Phoenix
Phoenix, A.Z. Photo by Elisabeth Gawthrop.
by ELISABETH GAWTHROP | Aug. 10, 2022
Phoenix is getting hotter. Climate change is a contributing factor, and so is the urban heat island effect. Scientists have known for at least 20 years that the sprawl of concrete and lack of significant green infrastructure has been making the city hotter, especially at night, but unchecked development has continued.
APM Research Lab has been collaborating with the Guardian to dive deeper into the temperature and health data in Phoenix, and connect the data with what people in the city are experiencing in day-to-day life. Read on for data examining how this summer (so far) compares to the past, and an hour-by-hour look at temperatures and 911 calls during a heat wave in June. Plus, more charts powered by APM Research Lab in the latest Guardian piece here.
Record-breaking nighttime heat this summer
Heat-related deaths have been increasing in Phoenix and its surrounding cities, particularly in the last five years. The heat itself isn’t the only factor that leads to increased deaths. Rising housing costs, cooling costs and opioid use are all intersecting risks that also contribute to more people in danger of getting sick from heat. But, the hotter temperatures do increase the amount of time people are at risk and the magnitude of that risk.
While extreme daytime temperatures topping 115ºF may grab the most headlines, hot nighttime temperatures are just as perilous because they don’t allow the body to recover. And nighttime temperatures in particular have been on the rise in Phoenix:
The average low temperature for June and July of this year was 84.3ºF. That’s warmer than any other year since 1950, just barely beating out 2006 (84.2ºF) and 2016 (84.1ºF).
The average high temperature for June and July of this year was 107.2ºF. That makes it the fifth hottest since 1950. The hottest year for high temperatures in June and July was 1978, with an average of 107.9ºF.
The hottest of the hot
An average high of 107ºF may already seem like extreme heat, but underlying that extreme might be different kinds of variability. It could mean there are a lot of days that are around the 107 mark, or it could mean there are a fair number of days that are cooler than that, and a similar number of days that are hotter than that.
We analyzed June and July Phoenix temperature data from 1950-2022 for the most extreme high temperatures — those above 110ºF and 115ºF. When looking at the number of days with temperatures at 110ºF or higher, this year ties with 1985 and 2008 for 9th hottest, with 20 such days. And when looking at the number of days reaching 115ºF or more, there has been just one such day this year, compared to six such days in June and July of the last two years. Not the most extreme year, but more extreme than anything seen between 1950 and 1973.
We did a similar analysis for nighttime temperatures, which you can see in the Guardian’s latest story. We found that in June and July of this year, there were 11 nights that didn’t dip below 90ºF. That ties with 2006 for the second-most number of extremely hot nights, with 2020 taking the top spot with 16 nights. This matters because the impact of heat is cumulative, and the body only starts to recover once it drops below 80ºF.
Hot nights coming earlier in the season
In addition to hotter temperatures, a lengthening heat season is also a risk from climate change.
This year saw the earliest night of 90ºF+ in the record books, which occurred on June 11. This earlier onset of the heat season has been especially pronounced over the last few years. Even as recently as 2016, the earliest night of 90ºF+ temperatures occurred on June 20.
Hourly 911 calls and temperatures during a hot period in June
No matter how you slice the data, the bottom line is that rising temperatures are impacting people’s health. In the Guardian’s latest story from Phoenix, it's clear that heat calls are placing a huge burden on the fire service, with crews responding to 34% more heat calls in June and July compared the same period in 2020.
Heat-related calls are coded as such by the Phoenix Fire Department, which handles medical 911 calls in the city. Here we show the hourly temperature and number of heat-related 911 calls for a two-week period in Phoenix in June 2022.
The most number of calls came during and after the hottest stretch of hourly temperatures, on June 11. The thermometer read 113-114ºF for four hours that afternoon.
Most calls were between 11 a.m. and 7 p.m. On many days, there are a number of calls in the 6 p.m. hour, which is just after many of the public cooling centers close. Overnight hours were for the most part quiet, with the exception of just after midnight on June 11. The temperature at that time was 100ºF.
APM Research Lab also examined the number of 911 calls related to heat since 2014, when the data began to be available. We found there have been just 3 days during the months of June and July since 2014 with no 911 calls for heat illness (June 6, 2015; July 23, 2021; July 25, 2021). And the most number of daily heat 911 calls so far in any year, any month, since 2014 was July 13 of this year, with 52 heat calls that day.
