Safe incubation is within those numbers:
This is from Brinsea. It is often better to simply post this stuff for all to see. It is from this pdf if you want to read the whole article
A review by H. Lundy of research carried out by a number of scientists over many years
identified five temperature zones each of which is characterized by its major affect on the
developing embryo. These zones are not clear cut. There is some overlapping and the time for
which the embryo is exposed and the age of the embryo blur the limits.
Lundy’s five incubation Temperature Zones:-
Zone of heat injury
Zone of hatching potential
Zone of disproportionate
development
Zone of suspended
development
Zone of cold injury
In common with most scientific work on incubation, this data assumes an incubator with a fan
(virtually no temperature differences within the incubator) and was based on chicken eggs.
These zones are further explained as follows:
Zone of heat injury (above 40.5°C/104.9°F)
At continuous temperatures above 40.5°C (104.9°F) no embryos would be expected to hatch.
However the effect of short periods of high temperature are not necessarily lethal. Embryos
up to 6 days are particularly susceptible, older embryos are more tolerant. For example,
embryos up to 5 days may well be killed by a few hours exposure to 41°C (105.8°F) but
approaching hatching time they may survive temperatures as high as 43.5°C (110°F) for
several hours.
Zone of hatching potential (35 - 40.5°C/104.9 - 84.5°F)
Within a range of 35 to 40.5°C (84.5 - 104.9°F) there is the possibility of eggs hatching. The
optimum (for hens) is 37.8 °C (100.4°F), above this temperature as well as a reduced hatch
there will be an increase in the number of crippled and deformed chicks. Above 40.5 °C
(104.9°F) no embryos will survive.