1 Nov 2013

Potten End Newsletter Article 12

This article originally appeared in the Potten End Newsletter, November 2013.

Potten End Weather

“October extinguished itself in a rush of howling winds and driving rain and November arrived, cold as frozen iron, with hard frosts every morning and icy drafts that bit at exposed hands and faces.”
― J.K. Rowling, Harry Potter and the Order of the Phoenix

After a calm, mild start, this October turned blustery, cold, and wet. At the time of writing we’ve yet to experience frost. I’m sure we’ll get some frost before October ends and we’ll definitely get it in November.

Forecasting frost more than a few days in advance is incredibly difficult due to the wide range of conditions that affect air temperature. For example, on cloudy nights the cloud can act like a duvet, trapping warmer air near the surface which makes it unlikely that frost will occur.

Did you know there are three types of frost that form in very different ways?

Air Frost

An air frost occurs when air which is at least one metre above the ground cools below the freezing point of water.

Ground Frost

When the surface temperature of the ground, trees, hedges or other objects falls below the freezing point of water, frost forms on the surface of these objects. Some surfaces are more prone to frost than others. For example, grass is more prone to frost than concrete or tarmac surfaces because concrete and tarmac hold on to heat more than grass.

It is possible for ground frost to occur even if the air temperature is above freezing. The ground and other objects radiate heat away at night and can cool significantly even in late spring and early summer. This is why gardeners need to be wary of frosts until at least the end of May and perhaps slightly beyond.

Hoar Frost

Hoar frost occurs when dew freezes. Hoar frost is either a ‘feathery’ or a plain white frost of a more globular form.

When the temperature of the surface is below freezing before dew forms, the ‘feathery’ variety of hoar frost is created on the surface.

When the temperature of the surface falls below zero after the dew forms, the dew droplets freeze and the white globular hoar frost is created.

November Expectations

November temperatures can vary as wildly as they can in October. In 2010 November had a record high of 17.7°C at the start of the month and a record low of -6.1°C at the end of the month. The average November temperature is around 7°C.

We’ve recorded an average of just over 80mm rain in past Novembers with a high of 148mm in 2009 and a low of 29mm in 2011 which precluded our 2012 drought.

Have fun sweeping and raking up the leaves … or just wait until the wind blows them over to your neighbour!