If there are any inquisitive first-timers reading this, then particular focus should be paid to being adequately prepared for the late evening/night time/early morning temperature roughly between Loudeac and Carhaix on the outward leg, between Carhaix and St. Meen le Grand on the homeward leg, and in the Perche region.....(apart from 2007 when it was 14 degrees day and night), these stretches have always been much colder than anticipated when riding at night or early morning.
In 2003, the event took place at the tail end of a heatwave, with daytime temperatures in excess of 32 degrees Celsius. At night, the temperature plummeted, a real shock to the system, with a morale crushing effect. There was a hoar frost in the countryside leaving Loudeac on the way back.
In 2019, my Garmin registered an average of 6 degrees for the 80 kms leg between Loudeac and Carhaix, with a low reading of 4 degrees, it felt colder on the descents. On the homeward section the average was 7 degrees for 100 kms from Carhaix to St. Meen, with a low of 5 degrees. After Mortagne, the mercury dropped to 6 degrees for 20/30 kms. It always feels colder though.
As mentioned above, the daytime temps were easily around 25 degrees.
When the body and mind are tired and sleep deprived, these fluctuations can have a dramatic effect on mood and resolve, so my tip is, at the very least, to take a lightweight/packable gilet with some thermal quality to counteract the adverse physical and mental effects of the cold.