Calculation of relative humidity

Relative humidity from dry bulb and wet bulb depression
	Web bulb depression in °C: Dry bulb minus the wet bulb
Dry bulb T in °C	0.5	1.0	2.0	2.5	3.0	3.5	4.0	5.0
21	95%	90%	83%	79%	77%	72%	67%	60%
24	96%	91%	84%	80%	78%	74%	69%	62%
27	96%	91%	85%	81%	78%	75%	71%	65%
28	96%	93%	85%	82%	78%	75%	72%	65%
29	96%	93%	88%	84%	80%	76%	73%	66%
30	96%	93%	86%	82%	79%	76%	73%	67%
32	96%	93%	89%	85%	81%	78%	74%	68%
35	96%	93%	89%	85%	82%	79%	75%	69%
38	96%	93%	89%	86%	83%	80%	76%	71%

Calculation of heat index

Heat index as an effective temperature in °C given a dry bulb temp. and Rel. Hum.
Relative humidity	21	24	27	28	29	30	31	32	35
	Dry bulb temperature in °C
60%	21	24	28	29.5	32	33	35	38	46
70%	21	25	29	30.7	34	35	37	41	51
80%	22	26	30	32.1	36	38	40	45	58
90%	22	26	31	33.7	39	41	43	50	64
100%	22	27	33	35.6	42	44	49	54	72

Effective temperature in °C:	Risk level
Less than 32 °C	Low risk: Safe to exercise with proper hydration
32 °C to 41 °C	Moderate risk: Heat cramps or heat exhaustion likely
Above 41 °C	High risk: Heat stroke likely.