Climate averages 1991–2020

Harrow weather
in May.

A mild, moderately wet month: the 5th warmest and the 5th driest of the year.

Long-term climate patterns, not a forecast for a particular trip.

Average high 16.1°C Daytime mean, May

Average low 8.2°C Night-time mean, May

Rainfall 52 mm 10 days with ≥1 mm

Daylight 16 h Sunrise to sunset, per day

May is a mild month in Harrow: daytime highs average 16.1°C and nights cool to about 8.2°C. By daytime temperature it is the 5th warmest of the 12 months.

Expect about 52 mm of rain on roughly 10 days, which makes May a moderately wet month (the 5th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 15 h 35 min on an average May day.

The nearest other city in this atlas is Hayes (9 km away). In May its highs average 16.3°C, about as warm as Harrow, with 52 mm of rain.

Among the 143 cities listed in the United Kingdom, Harrow ranks joint 25th of 143 for the warmest May highs and joint 27th of 143 for the driest May (rainfall, lowest first). The mean May high of those 143 cities is 15.2°C; Harrow is 0.9°C warmer than that mean.

From May to June, average highs rise by 2.9°C to 19.0°C, and monthly rainfall rises from 52 mm to 56 mm.

The annual picture

May in context

30-year average

Average highAverage low°C

Monthly rainfall

Average total · mm

Averages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated

Every month, side by side

Harrow climate table

1991–2020

Monthly climate averages for Harrow, 1991–2020
Month	Average highHigh / low	Average low	Rainfall mm/month	Rain days ≥1 mm/day	Daylight hours/dayDaylight h/day
January	7.1°C2.3°C	2.3°C	55	10.9	8.48 h
February	7.6°C2.2°C	2.2°C	45	9.4	9.910 h
March	10.0°C3.4°C	3.4°C	42	10.2	11.812 h
April	13.0°C5.1°C	5.1°C	49	10.9	13.814 h
May, selected	16.1°C8.2°C	8.2°C	52	9.8	15.616 h
June	19.0°C11.2°C	11.2°C	56	10.0	16.617 h
July	21.2°C13.4°C	13.4°C	54	10.6	16.116 h
August	20.8°C13.3°C	13.3°C	61	10.2	14.615 h
September	18.1°C11.1°C	11.1°C	47	9.0	12.713 h
October	14.2°C8.4°C	8.4°C	58	11.2	10.711 h
November	10.0°C5.1°C	5.1°C	63	11.0	8.99 h
December	7.4°C2.9°C	2.9°C	58	11.2	7.98 h

Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.

Compare places

May in nearby cities

Distance from Harrow

Read the numbers correctly

Climate, not a promise.

These patterns help compare months. They cannot tell you the weather on a specific day of your trip.

Sources, method and limits

How these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Harrow) is explained once on the Harrow year overview and on the Sources, method and limits page.

London, Archway and Fulham lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.