Environment Agency staff have spent the day dealing with an emergency at a canal in Grantham after hundreds of dead fish were discovered this morning.
It's thought they died through lack of oxygen caused by the hot weather.
Chemicals have now been added to the water to bring the oxygen levels back to normal.
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East Midlands weather: Starting dry, with clouds thickening
West Midlands weather: Staying dry overnight with some patchy amounts of cloud and clear spells developing