Rapid temperature fluctuations prevent a negative pressure in watches, which can create condensation. If this happens, you will see drops under the glass. Take the watch to a watchmaker immediately who can open and dry it out. The moisture does not disappear even if the dew disappears, so if this is not done, the moisture will remain in the movement, which can cause serious damage. Watches are not condensation-proof even if they are waterproof. Condensation can occur if you go from hot to cold temperatures or vice versa. For example from laying in the hot sun to diving into the chilly water. Condensation occurring is not necessarily a manufacturing defect and is therefore not a warranty issue.