A sudden heatwave can turn even the healthiest lavender bush completely odorless overnight. When temperatures soar, the plant isn't dying. It is actively venting off its volatile oils to protect its foliage from intense thermal stress.
The natural instinct is to rush out and dump water on the soil at midday, but that only worsens root stress and delays scent production. Rebuilding those lost aromatic compounds requires working with the plant's natural biology rather than fighting it.