A WBT of 30-35°C is dangerous. If you're engaged in physical activity, 27°C or above can be dangerous. 33°C is dangerous even for if you're naked and lying in the shade. Wikipedia says 35°C. At that temperature you literally cannot cool off (without A/C) -- perspiration can't evaporate fast enough; you start to be cooked. Not good if you're poor or don't have electricity (300 M people do not), or you can't afford an A/C.
A sustained wet-bulb temperature exceeding 35 °C (95 °F) is likely to be fatal even to fit and healthy people, unclothed in the shade next to a fan; at this temperature our bodies switch from shedding heat to the environment, to gaining heat from it. Thus 35 °C is the threshold beyond which the body is no longer able to adequately cool itself.Given the temperature, humidity and surface pressure, this NOAA site returns the WBT. I wrote about WBTs for last year's heat wave in the Persian Gulf here.
I used recent data from Wunderground for Titlagarh, India, in southeastern India, which I read was having a heat wave. (People cannot go out in the street during the day; social events have to take place in the evenings. 99 deaths so far.) On April 24th, their high temperature was 119°F (48.3°C), and their wet bulb temperature reached about 32.4°C. On April 26th it was 113 F° (45.0°C) but more humid, with a WBT of 32.8°C.
And it's only April.
N.b. You really need to know temperature, relative humidity and surface pressure as functions of time; the weather site only gives daily highs, daily lows, and daily aveages. In the above I used the high relative humidities for the day, and the high surface pressure.
With the high temperaure and average RH and average pressure, the numbers are 29,2°C and 31.4°C respectively -- still dangerous.