The Saumos fire acquired a second front above the trees. French officials said its smoke column became a thunderstorm, producing lightning and erratic winds over the fire line. [E4] Heat rising from the blaze drove the convection; the resulting outflow could then change the direction and speed of the burn below. [E4]
Gironde’s prefecture measured 42,000 hectares burned at its 13:00 update on Sunday. The response had grown to 2,500 firefighters and 18 aerial assets, backed by 1,500 military personnel and 1,200 police and gendarmes. [E1] Those forces were working a perimeter whose weather could no longer be treated as an external input.
Nearly 220,000 preventive evacuations had been ordered across 23 communes since the fire began. [E2] That figure is cumulative, not a count of people simultaneously displaced. It measures the repeated movement of people as the perimeter expanded.
Monday gave crews a narrower problem than the weekend had delivered. A steady night can hold a line; it cannot certify the next afternoon. The force on the ground still had to manage a fire large enough to alter the air above it.
Forecasters expected temperatures to climb again on Tuesday, with readings near 40 degrees Celsius possible in the region. [E3] The boring case is that crews hold the perimeter and keep the self-generated weather from recurring. Hotter air still removes part of the margin they gained overnight.
The next event is therefore smaller than another evacuation order and more consequential than another aerial image. Crews must keep every quiet segment quiet while the temperature climbs. Tuesday’s heat is the tripwire.