Temperatures in the Arctic Circle are likely to have hit an all-time record on Saturday, reaching a scorching 38C (100F) in Verkhoyansk, a Siberian town.     The record still needs to be verified, but it appears to have been 18C higher than the average maximum daily temperature in June. Hot summer weather is not uncommon in the Arctic Circle, but recent months have seen abnormally high temperatures. The Arctic is believed to be warming twice as fast as the global average