Valleys normally have up-valley winds from one to four hours after sunrise to about one hour before sunset.
Down-valley winds start one to three hours after sunset and, with favorable conditions of light winds and clear
skies, persist until one to two hours after sunrise.
Up-slope winds are caused by the sun heating the earth. Normally up-slope winds occur during the day and
down-slope winds at night as shown in Figure 6. Land and sea breezes (Figure 7) are also caused by the sun. Sea
breezes normally occur during the day and land breezes at night.
Figure 6. Up-slope and down-slope winds.