To top up even in warm weather, you need to use a mixture of antifreeze and distilled water.
Note: In extreme cases, to continue the trip, especially in warm weather, you can add clean water to the system. At the first opportunity, check the coolant density and adjust it.
Option for placement - radiator
Option for placement - partition
The coolant level on a cold engine (coolant temperature around +20°C) should be at the mark on the expansion tank or slightly higher.
Add cold coolant only to a cold engine to prevent engine damage.
Warning: Do not open the expansion tank cap on a hot engine - this is dangerous, as the cooling system is under pressure. The cap can only be opened when the coolant temperature is below 60°C. When opening, cover the cap with a rag.
When opening the expansion tank cap, first turn it slightly and release the pressure. Then carefully turn the cap further and remove it.