The Napier grounds have seen little appreciable rain this year, the most noticeable being drought-breaking day of a one-day cricket international which was scheduled for McLean Park on January 28.
The match between New Zealand and Pakistan had to be cancelled, without a ball being bowled.
Mr Olsen said Napier could do with 50mm of rain over three days, and then more to follow. Napier has had just 47mm of rain since the last weekend of March, when about 23mm fell in one day.
Although much of Hawke's Bay awoke to a frost yesterday, it warmed during a clear and sunny day for Napier to be put in the unusual position of having among the lowest and the warmest town or city temperatures in the 24 hours to 6pm.
According to MetService figures, temperatures in the Napier-Hastings area ranged from -2deg in Hastings shortly before dawn yesterday to 17.1deg in Napier mid-afternoon.
Frosts were recorded in Hawke's Bay from North to south, with a -0.1 minimum in Wairoa, -1.1 on the Takapau Plains and -0.6 in Dannevirke.
Warmer temperatures are forecast in Hawke's Bay for the rest of this week, with clear skies and light winds today, and mostly sunny with northwest winds tomorrow.