He said a lot of the rise was to do with interest rates remaining low and investors buying shares in New Zealand companies for strong dividend yields.
But investors were still looking for strong profit growth.
"Investors are looking for high single digit growth."
Williamson said if companies didn't achieve that there would be a risk that share prices would be hit.
He said close attention would be paid to what directors said in any forward looking statements.
"They will want to see pretty positive guidance that trading conditions remain good."
Williamson said companies linked to the tourism sector were expected to have a good result.
Those included Auckland Airport and Air New Zealand which has already given upgraded guidance on its result.
But Williamson said there were also some companies which benefited from the flow-on effect like Colonial Motors who sold cars to tourism companies.
"That sector should be doing pretty well."
He said businesses exposed to the local economy should also have a solid performance with the New Zealand economy humming along.
But the sector where pressure is most likely to be felt is the building sector.
Fletcher Building has already signalled its profits will be well down on what it expected earlier in the year.
Williamson said others like Metro Performance Glass and Steel & Tube may also be feeling the pressure.
Despite the building boom in New Zealand Williamson said the sector was facing capability restraints.
"It is certainly what has hit Fletcher Building. The margins are not fantastic and that has certainly put a bit of pressure on."
Brian Stewart, senior analyst strategy at Forsyth Barr, said strong migration had been a big driver in the economy in the last six months and that should be good for New Zealand focused companies.
Stewart said the retail sector would face ongoing pressure from online retailing.
"Realistically online in general makes that segment tougher."
The growth of online sales put pricing pressure on companies but some companies like Briscoe Group were still doing well.
"In general we would expect some revenue growth."
The issue was whether that translated to earnings growth, he said.
The New Zealand market had done high single digit growth last year but he expected it to be more mid-single digit growth this time around.
He said investors would be looking to see how company profits had been affected by labour cost increases.
The labour market was very heated in certain areas like construction.
Elsewhere it was less heated but unemployment was relatively low which meant companies were going to start having to pay up to get more people, he said.
Stewart said that would hit company bottom lines unless they could increase pricing but the rise in disruptive technologies tended to make it harder for companies to increase their prices.
"We will be looking at how that plays through."
Stewart said he expected international investors to remain supportive of the New Zealand share market while the economy remained strong.
"Unless we get a massive risk-off event I don't see them changing their investment view."
Around 50 per cent of the free-float of the New Zealand market was owned by international investors.
But he said there was always a risk that other economies could grow faster than New Zealand attracting international investors away.
"The New Zealand market is a more defensive market. If growth started to accelerate globally and investors wanted to get exposure - we just don't have that many companies that fit into that."
The generally accepted rule is that companies will release a profit forecast update if their profit is likely to be either 10 per cent or more above or below expectations.
But Stewart said companies may still see their share prices hit if they come out slightly below expectations or even in line with forecasts.
Australian investors tended to be much more brutal in punishing companies which did not report higher profits and around 15 per cent of the share market's free float was owned by Australian investors, he said.
"They are an unforgiving lot."
The higher the expectation the more likely a small disappointment or even a company meeting forecasts could be hit.
"When you have got high expectations even meeting forecasts may not be enough."
What's coming up
August 9: Sky City Entertainment Group
August 14: Contact Energy, Freightways
August 16: Fletcher Building
August 18: Spark New Zealand
August 23: Air New Zealand, Auckland International Airport
August 24: Meridian Energy, TradeMe