Heavy rain during the past few days means this month is on track to end up wetter than July 1976.
An average 44mm of rain fell across the UK from July 1 to July 28, according to provisional figures from the Met Office.
The total for the whole of July 1976, when the UK was in the middle of a blistering heatwave, was 43.3mm.
With further rain forecast on its way this week, the final total for July 2018 could be even higher.
Up to July 28, the UK had received just 56% of its average for the month.
Hertfordshire had enjoyed just 18%, while Essex had received only 19%.
The driest ever July was in 1955, when an average of 30.6mm rainfall was measured across the UK.
Comparable records for rainfall date back to 1910.
Meanwhile hot weather is forecast to return to parts of the country later this week, the Met Office said.
The south and east of the UK could see temperatures rise to the low 30s by the weekend.
An area of high pressure will settle over the UK this week. If it persists, hot conditions could continue at least to the start of next week and possibly into the middle of August, the Met Office added.
