Medical experts say there's been a four-fold rise in the number of Welsh cases of measles this year, compared to the previous 12 months.
From January to June there were 61 cases.
Public Health Wales says raising MMR vaccination rates is the key to tackling the problem.
Incidences of whooping cough were also up.
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Breezy overnight. It will become fairly cloudy as the night progresses.
It should turn cloudier through the early hours with some patchy drizzle and some hill fog too.
It will be a breezy day with variable amounts of cloud and some bright or sunny spells.