KEY POINTS:
Yesterday may possibly have been the hottest day of 2009...just 8 days into the year!
Temperatures up to 42 degrees were recorded in Christchurch yesterday afternoon as a light nor'wester combined with blue skies and a scorching hot sun.
Quite a few people have written to me asking why the 'official' national highs were several degrees lower. Well, that's simply because you have the true air temperature and then the localised temperatures.
The true air temperature is the one that the atmosphere and land create naturally. This is recorded in a specially designed white box that allows the air to move through it, but limits the effects of the wind.
It's placed over grassy flat land, almost always at an airport. This is common throughout the world. It's the most accurate way of measuring the true air temperature.
The localised temperatures are, I guess to put to it crudely, the 'polluted' data. By 'polluted' I mean concrete driveways, tarseal roads, metal roofs etc...they all combine to create the temperature that YOU actually feel - and in summer they raise the temperatures several degrees over the airport readings.
Now as far as MetService and NIWA go they have to rely on pure data, not interrupted by mankind structures nearby. This is how you work out average temperatures and of course any climate change.
But as far as you and me go, it almost has no relevance on our every day lives. Humidity, windchill, wind speeds, the buildings around us, the colour of the sand we're on at the beach, the exposed nature of where we are - they all combine to create the air temperature we actually FEEL on our skin.
So I tend to ignore those "official" readings and I go by the two other alternatives - 1) The private weather stations that people have in their backyards. 2) The "Feels like" temperatures which records humidity and wind chill.
Yesterday's highs in the early 40s in Christchurch and the low 30s in Auckland and Waikato, Gisborne and Hawkes Bay were all accurate. A thermometer simply can't lie!
If the mercury says it's 40 degrees then that's what it is - whether it's artificial (caused by your hot driveway, patio or buildings nearby) or not.
If you put a thermometer out on your concrete driveway and it says 51 degrees...then that is what is! It's no wonder walking barefoot across the road to buy that ice cream hurt so much!
And why you spent 20 minutes in the shower last night trying to remove tar from the soles of your feet!! (been there, done that, almost every summer)
Today we can expect another hot one, perhaps not reaching the levels we saw yesterday - the hottest day in Christchurch so far this century! (wow, sensational!).
Sub-tropical low
The sub-tropical low I alluded to earlier this week - and mentioned in the Herald yesterday - is still developing but there's good and bad news.
The good news for holidaymakers is that it's definitely going to track well east of New Zealand so easterlies may be a little breezy at times this weekend along with a few showers and drizzle patches.
The bad news for farmers in Gisborne is that it won't bring much relief to you.
Cricket in Auckland
As I write this blog there's a 40 to 50 per cent chance of showers on Saturday in Auckland. As terrible as it sounds coming from a forecaster, I think there's a 50/50 chance of the cricket happening tomorrow.
I know that's a politician's answer but I'm not the one making the decision as to whether or not play will go ahead. If it was up to me I'd play in the rain...then I could say there's a 100 per cent chance it will go ahead!
Photo: Lily Hardy adds the finishing touches to a sandcastle 'crocodile' on the beach at Te Arai Pt, Northland. Taken by Deb Hardy. See all the pictures in the Herald summer picture competition here
