HeatRisk Maps | Historical HeatRisk Data |
No risk. | Risk to those extremely sensitive to heat. | Risk to those sensitive to heat. | Risk to most people. | Risk to everyone. |
None | Low | Moderate | High | Very High |
Daily Record High Maximum Temperatures | ||||||
Daily Record Warm Minimum Temperatures | ||||||
Above: 33%
Near: 33%
Below: 33%
Probability of the average temperature during next week being above, near, or below normal. Get more from the NOAA/Climate Prediction Center |
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Heat is the deadliest weather in Arizona. During Arizona's hottest months, the NWS issues alerts to notify the public when unusually hot weather is expected. These alerts are intended to raise awareness and prevent heat illness and death from occurring and mitigate financial impacts. When the NWS issues an alert, it should serve as a signal that on that day it is not "business as usual."
Collaborative research with the Centers for Disease Control and Prevention (CDC) shows that heat-associated deaths in Arizona can occur with temperatures in the mid 80s and hotter. Research also shows that our bodies have a greater ability to tolerate heat as the summer wears on, known as acclimation. For example, a temperature of 105 °F in May will seem hot, whereas the same temperature in June or July will not seem as hot because our bodies have acclimated to the heat. Hence, there is not one single, constant temperature used to determine when an alert will be issued. In order to better address heat risk and allow you to prepare for upcoming heat events, the NWS developed the experimental HeatRisk product.
Level 0 (Green): No elevated risk. | Level 1 (Yellow): Low Risk for those extremely sensitive to heat, especially those without effective cooling and/or adequate hydration. | Level 2 (Orange): Moderate Risk for those who are sensitive to heat, especially those without effective cooling and/or adequate hydration. | Level 3 (Red): High Risk for much of the population, especially those who are heat sensitive and those without effective cooling and/or adequate hydration. | Level 4 (Magenta): Very High Risk for entire population due to long duration heat, with little to no relief overnight. |
HeatRisk provides a quick view of potentially impactful heat conditions over the upcoming seven days based on how much above normal high and low temperatures are, the duration of unusual heat, and humidity (as represented by overnight low temperatures). HeatRisk is portrayed in a numeric (0-4) and color (green/yellow/orange/red/magenta) scale which is similar in approach to the Air Quality Index (AQI) or the UV Index. It provides one value each day that indicates the approximate level of heat risk concern for any location, along with identifying the groups who are most at risk. This product is complementary to the official NWS Watch/Warning/Advisory program and is meant to provide continuously available heat risk guidance for those decision makers and heat sensitive populations who need to take actions at levels that may be below current NWS heat product levels.
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HeatRisk temperature thresholds for Phoenix Sky Harbor International Airport. Click image for full version. Other locations available here. |
When "High" or "Very High" HeatRisk conditions are forecast, an Excessive Heat Watch or Excessive Heat Warning will be issued. An Excessive Heat Watch conveys a moderate (50%) confidence that excessive heat will occur. If confidence increases to a high (80%+) level, an Excessive Heat Warning is issued. Both alerts are a way to give public and emergency officials a "heads up" that extreme temperatures are expected. Additional information may be found here. Note that many lower elevation locations across the Southwest which experience chronic heat do not receive the lesser Heat Advisory alert.
Based on an analysis of emergency room visits across Maricopa County during 2020, it was found that HeatRisk categories accurately describe the level of heat-related illness. During the hottest days, with "High" and "Very High" HeatRisk categories, spikes in ER visits were noted. These days were generally coincident with the issuance of Excessive Heat Warnings. For lower risk days, ER visits were still noted but to a lesser degree. When averaging by HeatRisk category, there is a steady increase in ER visits for heat-related illness as intensity levels increase. Notably, heat-related illness was observed even on "Low" days, clearly indicating that even without official alerts heat can pose a significant health threat if precautions are not taken.
Preventing Heat-Related Illness
Your body keeps itself cool by letting heat escape through the skin, and by evaporating sweat (perspiration). If your body does not cool properly or does not cool enough, you might suffer from a heat-related illness.
Anyone can be susceptible to heat-related illness. Those at greatest risk are infants and young children, adults over 65, people who are homeless, people who are overweight, people who overexert during work or exercise, and people who are physically ill or on certain medications, such as for depression, insomnia, or poor circulation. Heat-related illness may be serious or even deadly if unattended.
Staying healthy during the summer is easier if you take the time to protect yourself by making sure you are drinking enough water and limiting your exposure to the heat. Follow these simple rules:
Signs & Symptoms of Heat-Related Illness
When temperatures are on the rise, watch for the following symptoms:
Stages of Heat-Related Illness
Heat-related illness usually comes in stages. The signal of the first stage is thirst. Drinking water at this stage can prevent you from progressing to the more serious kinds of heat related illnesses. The next stage is muscle cramps. These cramps can be mild or very painful. If you are caring for a person who has heat cramps, have him or her stop activity and rest. If the person is fully awake and alert, have him or her drink small amounts of cool water or a commercial sports drink. Gently stretch the cramped muscle and hold the stretch for about 20 seconds, then gently massage the muscle. Repeat these steps if necessary. If the victim has no other signals of heat-related illness, the person may resume activity after the cramps stop.
The signals of the next, more serious stage of a heat-related illness (often called heat exhaustion) include:
The warning signs of the most serious stage of a heat-related illness (often called heat stroke or sun stroke) vary but may include:
NOTE: Heat stroke is life threatening. Call 9-1-1 or the local emergency number if you are suffering from any of the above symptoms.
General Care for Heat Emergencies
General care for heat emergencies include cooling the body, giving fluids, and minimizing shock. For specific heat-related emergencies, follow these steps:
Additional Resources:
ADHS Extreme Weather & Public Health | CalOES Summer Heat Resources | CDC Extreme Heat | EPA Extreme Heat
Phoenix, AZ Area
2022 (5): June 8-12
2021 (20): June 12-20, July 9-11, August 3-4, August 25-27, September 9, September 12-13
2020 (48): April 26-30, May 6-7, May 27-31, June 2-4, July 10-13, July 19, July 29-August 4, August 9-10, August 12-20, August 24-28, September 4-7, September 17
2019 (26): June 11-13, July 11-16, July 27-28, August 3-5, August 13-16, August 20-21, August 27-28, August 30-31, September 4, September 7
2018 (16): May 6, June 3-4, June 12-13, June 21-22, July 5-6, July 23-25, August 6-7, September 14-15
2017 (19): June 4-7, June 17-26, July 5-7, August 29-30
2016 (11): June 3-6, June 19-23, July 22-23
2015 (14): June 16-22, August 4-5, August 13-17
2014 (8): June 2-5, July 23-24, July 30-31
2013 (15): June 2, June 7, June 12, June 28-July 3, August 1, August 16-19, August 20
2012 (20): May 21-22, May 31-June 1, June 18, June 27-30, July 9-10, August 6-14
2011 (22): June 22, June 27-29, July 1-3, August 2-3, August 18, August 22-September 1, September 4
2010 (25): June 6-7, June 30-July 2, July 8-10, July 13-21, August 5, August 13-15, August 23-25, September 3
2009 (21): July 11-14, July 17-20, July 26-29, August 2-6, August 27-30
2008 (18): May 19-20, June 15-23, July 1-3, July 18, July 31-August 2
Yuma, AZ Area
2022 (4): June 9-12
2021 (11): June 12-20, June 27-28, July 9-11, August 3-5
2020 (38): April 26-30, May 6-7, May 27-29, June 3-4, July 11-13, July 19, July 30-August 3, August 13-20, August 24-27, September 4-7, September 17
2019 (18): June 11-13, July 12, July 15-16, August 3-5, August 13-16, August 20-21, August 30-31, September 4
2018 (7): May 6, June 13, June 22, July 5-6, August 6, September 8
2017 (15): June 17-26, July 7, August 27-30
2016 (9): June 3-5, June 19-22, July 22-23
2015 (14): June 16-22, August 4-5, August 13-17
2014 (5): Jul 23, Jul 24, Jul 30, Jul 31, August 30
2013 (8): June 7, Jun 28-July 3, August 17
2012 (17): May 13-14, May 21-22, May 31-June 1, June 18, July 9-11, August 8-14
2011 (8): June 28, July 2-3, August 2-4, August 29, September 08
2010 (6): July 17-18, August 24-25, September 3-4
2009 (17): July 11-14, July 17-20, July 26-29, August 05, August 27-30
2008 (21): May 18-20, June 14-23, June 30-July 03, July 18, August 1-2, September 6
El Centro, CA Area
2022 (4): June 9-12
2021 (14): June 2-4, June 12-20, June 27-28, July 9-12, August 3-5
2020 (37): April 26-30, May 6-7, May 27-29, June 3-4, July 11-13, July 30-August 3, August 13-20, August 24-27, September 4-7, September 17
2019 (20): June 11-12, July 12-16, July 28, August 3-5, August 13-16, August 20-21,August 30-31, September 4
2018 (14): May 9, June 3-4, June 13, June 22, July 6, July 23-27, August 6-7, September 8
2017 (13): June 18-25, July 7, August 27-30
2016 (15): June 3-5, June 19-22, June 29, July 22-23, July 27-28, August 15-17
2015 (14): June 16-22, August 4-5, August 13-17
2014 (5): July 23-24, July 30-31, August 30
2013 (8): June 7, June 28-July 3, August 17
2012 (17): May 13-14, May 21-22, May 31-June 1, June 18, July 9-11, August 8-14
2011 (5): June 28, July 2, August 4, August 29, September 8
2010 (6): July 17-18, August 24-25, September 3-4
2009 (17): July 11-14, July 17-20, July 26-29, August 5, August 27-30
2008 (21): May 18-20, June 14-23, June 30-July 3, July 18, August 1-2, September 6