National Weather Service United States Department of Commerce


hot sun pic

NOAA's National Weather Service Heat Page

Heat index chart

Heat Index Calculator
Choose the appropriate calculator and enter the values. Then click "Calculate".
Using Dew Point Temperature Using Relative Humidity
Air Temperature
oF oC
Dew Point Temperature
oF oC

Heat Index =

  Air Temperature
°F °C
Relative Humidity


Heat Index =

* Please note: The Heat Index calculation may produce meaningless results for temperatures and dew points outside of the range depicted on the Heat Index Chart above.


Heat Wave:  At least 3 consecutive days with high temperatures of at least 90 degrees.

Highest Temperatures:  Mid July through mid August across interior locations. 

Heat Index:  An estimate of how hot it feels when air temperature and humidity are combined.

Heat Advisory:  Issued when the heat index is forecast to reach 95 to 99F for at least 2 consecutive days or 100 to 104F for any length of time.

Excessive Heat:  Issued when heat index values are forecast to reach or exceed 105°F for at least 2 consecutive hours.
   Watch is issued 24 to 48 hours of the event. 
   Warning is issued within 24 hours of the event.


NWS Products for Heat Emergency Planning


Short Range Forecasts - National Weather Service - New York, NY

Excessive Heat Outlooks:  Contained in the Hazardous Weather Outlook (HWO)

     Days 2 to 7 Section, 3 to 5 days before the anticipated event: 

Excessive Heat Watches:  Issued as Non-Precip Watch (NPW) 24 to 48 hours before event.
Excessive Heat Warnings:  Issued as Non-Precip Warning (NPW) within 24 hours of event.

Heat Advisories:  Issued as Non-Precip Warning (NPW) within 24 hours of event.

3 Hour Heat Index (Apparent Temperature) Forecasts through Day 3 (Next 72 hours)

Hourly Observations (heat index values of at least 90 degrees will appear in remarks section).

Medium Range Forecasts - Weather Prediction Center's Outlooks

Days 3-7 Heat Index Forecasts for New York City

Daily Maximum Heat Index Forecasts:  Chance of Heat Index Reaching 95, 100, and 105.   

Daily Mean Heat Index Forecasts:  Chance of Heat Index Reaching 85, 90, and 95 degrees.

Daily Minimum Heat Index Forecasts:  Chance of Heat Index Reaching 75, 80, and 85 degrees.

Long Range Forecasts - Climate Prediction Center's National Outlooks

Seasonal Temperature & Precipitation Outlooks for NYC

National Outlooks


Central Park Climatology

Daily Normal Max T
Daily Record Max T
90 Degree + Days by Month/Year
90 Degree+ Day Facts
100+ Days by Month/Year

Heat Wave Safety Tips

  • Slow down. Strenuous activities should be reduced, eliminated, or rescheduled to the coolest time of the day. Individuals at risk should stay in the coolest available place, not necessarily indoors.
  • Dress for summer. Lightweight, light-colored clothing reflects heat and sunlight, and helps your body maintain normal temperatures.
  • Foods (like proteins) that increase metabolic heat production also increase water loss.
  • Drink plenty of water or non-alcoholic fluids. Your body needs water to keep cool. Drink plenty of fluids even if you don't feel thirsty.
  • Do not drink alcoholic beverages.
  • Spend more time in air-conditioned places. Air conditioning in homes and other buildings markedly reduces danger from the heat. If you cannot afford an air conditioner, spending some time each day (during hot weather) in an air conditioned environment affords some protection.
  • Never leave persons, especially children, and pets in a closed, parked vehicle
  • Don't get too much sun. Sunburn makes the job of heat dissipation that much more difficult.


Additional Links

  • The Climate Explorer - Explore maps and graphs of historical and projected climate trends for the United States. View data by topics such as temperature to see how climate change will impact things you care about:

  • National Integrated Heat Health Information System (NIHHIS) - an integrated system that builds understanding of extreme heat, defines demand for climate services that enhance societal resilience, develops science-based products and services from a sustained climate science research program, and improves capacity, communication, and societal understanding of the problem in order to reduce morbidity and mortality due to extreme heat.



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