Heavy and thundery downpours developed over north-west England and north Wales around midday, spreading across North Yorkshire through the afternoon. The worst-affected areas were around the North York Moors, with flooding being reported in Helmsley and surrounding areas.

The following information is provisional from both our real-time network and hourly data obtained from the Environment Agency (indicated by a * in table below) on 20 June 2005.
From the station data available, Hawnby (north-west of Helmsley) has reported the most intense rainfall, including just over 50 mm in a 30-minute period.
The Hawnby 3-hour, 1-hour and 30-minute totals all generate return periods in excess of 200 years (using the Flood Estimation Handbook method).
| Hour ending in GMT | ||||||
|---|---|---|---|---|---|---|
| Station | 15 | 16 | 17 | 18 | 19 | Total rainfall |
| Hawnby (*) | - | 5.8 | 59.8 | 3.8 | - | 69.4 (3 hr) |
| Church Houses (*) | - | 0.6 | 27.0 | 16.1 | 0.4 | 44.1 (4 hr) |
| Topcliffe | 0.2 | 7.4 | 29.2 | 3.6 | 0.0 | 40.4 (4 hr) |
| Westerdale (*) | - | 1.8 | 27.2 | 7.0 | - | 36.0 (3 hr) |
| Brompton, Low Moor (*) | 19.0 | 13.8 | 0.4 | - | - | 33.2 (3 hr) |
| Dishforth Airfield | 0.0 | 6.0 | 16.4 | 3.0 | 0.0 | 25.4 (3 hr) |
| Osmotherley (*) | - | 12.0 | 9.2 | 1.0 | - | 22.2 (3 hr) |
| Lockwood (*) | - | 1.0 | 15.8 | 4.8 | - | 21.6 (3 hr) |
| Hawarden (N Wales) | 30.8 | 10.8 | 1.2 | 0.0 | 0.0 | 42.8 (3 hr) |
The UK record for a 30-minute period is 80 mm at Eskdalemuir, Dumfries and Galloway, 26 June 1953.
More-intense rainfalls have been recorded in North Yorkshire. For example, on 10 August 2003 (date that the UK temperature record of 38.5 °C was established), an intense rainstorm was recorded at Carlton-in-Cleveland (North Yorkshire). A total of 49.1 mm was recorded in 15 minutes, 45.9 mm in 10 minutes, 41.3 mm in 8 minutes and 30.0 mm in 5 minutes (information taken from a detailed report produced by the observer at the station, available in 'Weather', Vol. 60, March 2005). Carlton-in-Cleveland, reported 27 mm in 30 minutes during the 19 June 2005 event.
Tip-time data have been received from the Environment Agency for Hawnby, and has been plotted in 5-minute intervals below.

Radar imagery
The animation below uses 15-minute, 5 km composite data between 1200 GMT and 1800 GMT.

Initial analysis of 5 km radar data, indicates that some points may have had over 100 mm in just 3 to 4 hours.
Please note: The empirical relationship between radar reflectivity and rainfall rate is fixed whereas in reality this is highly dependent on precipitation type and is very different for rain and hail.