Wood burns better [more easily] when dry.

干柴好烧。

《新英汉大辞典》

Paint with orange paint, and remove tape when dry.

把罐子涂成桔黄色，等干了之后撕下胶带。

youdao

When the soil is dry, more moisture is lost from the plant.

土壤干燥时，植物就会失去更多的水分。

《柯林斯英汉双解大词典》

She says the only work needed once beets have been thinned is weeding and, when the weather is dry, a weekly watering.

VOA: special.2010.03.02

Scientists say the presence of iron in the rock shows that the weather was hot and dry when the rock was first formed.

VOA: special.2009.04.15

Hay has to be cut and gathered when it is dry.

VOA: special.2010.01.31

The new gum becomes non-adhesive when dry and decomposes to dust within six weeks, a spokesman for Mexico's Chicza Mayan Rainforest Chewing Gum told CNN.

CNN: New gum could mean sticky end for mess

Dr Lackner's version uses layers of Teflon or paper covered with a resin that absorbs carbon dioxide when dry and gives it up when moist.

ECONOMIST: Combating climate change

Dr Karp's patch mimics this action using minute needles made of plastic with tips that are rigid when dry but swell once they have pierced wet tissue.

BBC: 'Bed-of-needles' super-grip plaster for surgical wounds