Tuesday's 33.8°C was just 0.5 degree Celsius below the island's hottest ever recorded summer temperature.
Guernsey has broken its June temperature record two days in a row.
The previous high of 30.8°C was eclipsed by nearly 1.5C on Monday (22 June) and by 3°C on Tuesday (23 June).
Alderney, which is further into the cooling English Channel, hit 31°C yesterday, 10 degrees up on Monday's temperature.
It was much hotter in Jersey at 37.2°C as the heat dome effect over Europe continues to build.
In the southern UK, Network Rail wants people to use the trains only if they have to.
Islanders flying into Gatwick may face delays in their onward journey as the rail infrastructure warps in the heat.
France recorded its hottest ever day, south of Bordeaux, where it hit 44.3°C.
A nuclear reactor at a power plant that empties cooling water into the Garonne River near Bordeaux had to be closed down because it would have made the water too warm for the species living in it.
French authorities say 40 people have drowned while swimming unsupervised over the past few days and in Paris, the Eiffel Towel and the Louvre closed early, due to the intense heat.
Here, the lack of a breeze and the very high humidity - 89% according to the most recent Met aviation report for Guernsey - contribute to the feel that the temperature is far hotter.
The night-times are classed as tropical as they are hovering at or above 20°C.
The heatwave is forecast to peak on Thursday (25 June) and the temperature will fall away by around 10°C by Friday to 23°C.

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