Acesur, a supplier of the UK's biggest supermarkets, told the BBC this would feed into prices in shops in the next three to four months when companies renew their contracts.
The country, along with other parts of Western Europe that produce olive oil, including Italy and Portugal, has been experiencing extreme temperatures and a lack of rain in recent weeks.
Acesur produces more than 200,000 barrels of olive oil a year, out of the approximately 1.4 million barrels produced in Spain each year, and sells its products in more than 100 countries.
It sells around 20,000 tonnes a year in the UK and packs own-label brands for Asda, Waitrose, Morrisons and Sainsbury's. The supermarkets also stock the La Espanola brand, which is the third biggest in the UK.
Most of the olives in its products are grown in Andalucia, southern Spain, which has had very little rainfall in recent weeks.
Last year, Spain produced around 1.4 million tons of olive oil, but he said officials were now forecasting as little as one million tons for this season.
He said that the dry weather could also affect the crop if olive trees could not grow new branches due to lack of water.
This is having an impact on global prices. The Mintec benchmark price for extra virgin olive oil went to its highest level this year in July, up 7.3% on the previous month and 14.2% on the previous year, according to the market research group.
Colmenero said this would eventually feed into prices for customers, although there would be a three to four month lag because many companies would already have signed 12 month contracts with retailers.
He added that companies would have to raise their prices when they renewed contracts and customers could see increases of 20 -- 25%.
The average price of own-label olive oil in the four biggest UK supermarket chains was up 50.2% last year, according to retail research firm Assosia. Average prices went up 28.5% from June to July.
She said that if the grain corridor agreed from Ukraine resulted in more supplies of sunflower oil coming out of the country, this could bring some relief.