If you're commuting on SNCB trains, there's a good chance your train may not have air conditioning.
According to RTBF, 53% of SNCB trains have air conditioning, and air conditioned cars make two-thirds of journeys for SNCB.
"Most of them only make two trips a day, during rush hour," Elisa Roux, SNCB spokesperson, told RTBF about the older trains without air conditioning. "This old rolling stock is mainly used as a reinforcement, as an additional train to the basic offer."
RTBF reported that only 7 out of 17 train models have air conditioning and that there was no way to predict which trains would be on which routes.
The Brussels Times