FC, CC, and PH should be tested right away. PH shifts with temperature, and chlorine can actually evaporate right out of the sample container if you leave it sitting, in addition to being destroyed by sunlight. TA and CH don't really matter, though you may need to swirl the CH test longer at lower temperatures. CYA works more reliably at room temperature, though if you give it enough time to react it will work with cold water.