​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Weather & Warnings

Heat Index/Air Quality Forecast​​Climate Change graphics

Heat Index​

The heat index (also known as the apparent temperature) is what the temperature feels like to the human body when relative humidity is combined with the air temperature.  This has important considerations for the human body's comfort.

When the body gets too hot, it begins to perspire or sweat to cool itself off.  If the perspiration is not able to evaporate, the body cannot regulate its temperature.  Evaporation is a cooling process.  When perspiration is evaporated off the body, it effectively reduces the body's temperature.  

When the atmospheric moisture content (i.e. relative humidity) is high, the rate of evaporation from the body decreases.  In other words, the human body feels warmer in humid conditions.  The opposite is true when the relative humidity decreases because the rate of perspiration increases.  The body actually feels cooler in arid conditions.

There is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases).

For additional information on Heat Index, visit the National Weather Service website.

Air Quality Index​​

The Air Quality Index (AQI) is used for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. The Environmental Protection Agency (EPA) calculates the AQI for five major air pollutants regulated by the Clean Air Act: 

  • Ground-level ozone

  • Particle pollution (also known as particulate matter)

  • Carbon monoxide

  • Sulfur dioxide

  • Nitrogen dioxide. 

​For each of these pollutants, the EPA has established national air quality standards to protect public health .Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country.​

For additional information on AQI, visit the National Weather Service​website.

​Storm Ready​​​

Storm Ready logo

The City of Phoenix has been designated as being StormReady by the National Weather Service (NWS), which means Phoenix has reached a high level severe weather preparedness.


Approximately 98 percent of all Presidentially declared disasters are weather related, leading to around 500 deaths per year and nearly $15 billion in damage. The StormReady​ program helps the City of Phoenix to assist our community with the communication and safety skills needed to save lives and property--before, during and after the event. StormReady helps city leaders and emergency managers strengthen local safety programs.

StormReady communities are better prepared to save lives from the onslaught of severe weather through advanced planning, education and awareness. No community is storm proof, but StormReady can help communities save lives.

StormReady uses a grassroots approach to help communities develop plans to handle all types of extreme weather—from extreme heat to flooding. The program encourages communities to take a new, proactive approach to improving local hazardous weather operations by providing emergency managers with clear-cut guidelines on how to improve their hazardous weather operations. 


These are the guidelines the City of Phoenix abides by to be officially StormReady:

  • Established and maintains a 24-hour warning point and emergency operations center

  • Has more than one way to receive severe weather warnings and forecasts and to alert the public

  • Created a system that monitors weather conditions locally

  • Promotes the importance of public readiness through community seminars

  • Developed a formal hazardous weather plan, which includes training and exercise.

For additional information on StormReady, visit the National Weather Service website.


Steps To Take Before, During and After a Weather Event​

​Flood Resources​
​​​Heat Ready​
Monsoon Resources​​

Weather Disclaimer:
Weather data is provided as a general guide only. City of Phoenix assumes no responsibility for any loss resulting from use of this information. The user assumes the entire risk related to the use of this data. The City of Phoenix provides weather data through a third party "as is", and the City of Phoenix disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. In no event will the City of Phoenix be liable to you or to any third party for any direct, indirect, incidental, consequential, special or exemplary damages or lost profit resulting from any use or misuse of this data.​​

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