Heat Index Chart

Heat index (or apparent temperature) is how the heat and humidity in the air combine to make us feel. Higher humidity plus higher temperatures often combine to make us feel a perceived temperature that is higher than the actual air temperature. The old saying, "its not the heat, its the humidity" holds true. Sometimes in the summer in the North Sacramento Valley, our relative humidities are so low that we actual feel cooler! See the chart below showing various combinations of air temperature versus relative humidity to help you gauge for yourself.

Use the current temp and humidity from the screen above with the chart below

Heat Index Chart

% Relative Humidity

		15	20	25	30	35	40	45	50	55	60	65	70	75	80	85	90
T e m p e r a t u r e	110	108	112	117	123	130
	105	102	105	108	113	117	122	130
	100	97	98	102	104	107	110	115	120	126	132
	95	91	93	95	96	98	100	104	106	109	113	119	124	130
	90	86	87	88	90	91	92	95	97	98	100	103	106	110	114	117	121
	85	81	82	83	84	85	86	87	88	89	90	92	94	96	97	100	102
	80	76	77	78	78	79	79	80	81	82	83	84	85	86	87	88	89

Legend
80-89 degrees	Fatigue is possible with prolonged exposure and/or physical activity.
90-104 degrees	Sunstroke, heat cramps and heat exhaustion are possible with prolonged exposure and/or physical activity.
105-129 degrees	Sunstroke, heat cramps and heat exhaustion are likely. Heat stroke is possible with prolonged exposure and/or physical activity.
130+ degrees	Heatstroke/sunstroke is highly likely with continued exposure.

Above is a heat index (or apparent temperature) chart showing various combinations of air temperature versus relative humidity.

To use the chart, locate the air temperature along the left column and the relative humidity along the top. The cell where the two intersect is the heat index.

For example, an air temperature of 90 degrees Fahrenheit and a relative humidity of 60 percent intersect at a heat index of 100 degrees. In other words, the temperature would feel like 100 degrees with this humidity/temperature combination.

Heat index values were devised for shady light wind conditions. Exposure to full sunlight can increase values by up to 15 degrees Fahrenheit.

First aid treatment suggestions for heat-related illnesses can be obtained from local Red Cross offices, hospitals, clinics, public health agencies and physicians.

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