Can you please send photos of the symptoms on the cherrylaurel? They are not known to contract powdery mildew with any regularity, if at all. Neem oil is also not very effective as a fungicide compared with its use as an insecticide. Instead, cherrylaurel can get other leaf infections or outbreaks of scale insects on the bark. Here's more information:

https://marylandgrows.umd.edu/2019/01/07/qa-whats-wrong-with-my-cherry-laurel-shrubs/

https://marylandgrows.umd.edu/2019/09/25/qa-what-is-this-white-growth-on-my-cherry-laurel-shrub/

Pesticide sprays need to be applied according to directions on that product's label, as there isn't always a catch-all regarding conditions. (For instance, high humidity, stagnant air, and overcast skies might make accidental plant damage from an oil spray more likely, but that might not hold true about other ingredients. If the label doesn't specify this, weather may not be very restrictive.) In general, any foliar spray should be avoided during temperatures above 85 degrees as plant tissue damage may result, especially for oil-based sprays. Outside of this, time of day may not matter much so long as weather conditions (temperature, wind) are appropriate to reduce the risk of drift onto nearby plants. Usually, one wants plant foliage to be dry by nightfall to minimize the risk of fungal or bacterial infection.

Miri

Thank you for the photo. This plant is a Euonymus, not Cherrylaurel; both are very commonly used as hedging and foundation plants. It's likely the variety Euonymus kiautschovicus 'Manhattan', though that doesn't matter much with regards to the mildew. Euonymus are often afflicted with this fungal disease.

A number of general-purpose fungicide products should be labeled for use on powdery mildew. They won't cure existing infection so much as they will help prevent the spread of the fungus. Follow label instructions with regards to how and when to spray, and when to re-treat, since several applications will be needed to keep the mildew suppressed for the rest of the season. The shrub may shed some of the more heavily-damaged leaves, but if it remains healthy into next year, it will produce replacement growth. Avoid trimming the plant into too dense of a shape (such as from shearing), as this reduced air circulation among the foliage creates conditions conducive to infection.

https://extension.umd.edu/resource/powdery-mildew-disease-trees-and-shrubs

Miri