Met Éireann has flagged a potato blight warning window for northwest and western Ireland running from Saturday night into Sunday afternoon, alongside a weekend forecast of 13-20°C daytime highs and up to twice-average rainfall in south and east regions.

The national forecaster's update for Friday, September 25 and the days ahead maps mixed conditions with limited spraying opportunities. Monday stands out as the driest and brightest day in the seven-day window and the best chance for spray applications.

What's the day-by-day breakdown?

Friday, September 25 will be dry and bright in many areas after morning rain and drizzle in the south and east clears eastwards. Sunny spells and isolated showers dominate the afternoon, with showers becoming more frequent and heavy in the west and northwest later. Daytime highs range 13-18°C in light to moderate south-westerly breezes, fresher along western coasts.

Friday night stays dry in many places with scattered showers continuing in the west and northwest. Overnight lows sit at 9-13°C in light to moderate south-westerly winds.

Saturday brings more dry, bright weather with sunny spells and isolated showers, before more frequent showers develop in western and north-western areas later. Top temperatures reach 15-20°C in moderate to fresh south to south-westerly winds.

When does the blight pressure build?

Cloud increases on Saturday night and pushes rain into western and southern parts, with some heavy falls at times. Met Éireann has advised that weather conditions conducive to the spread of potato blight will occur in the northwest and west from Saturday night through Sunday afternoon — the same period when western areas see the heaviest rainfall.

Western potato growers should treat this as the highest-risk slot of the coming week. Southerly winds on Saturday night stay moderate to fresh. Sunday opens cloudy with outbreaks of rain turning heavy in places, clearing to scattered showers and sunny spells by afternoon. Daytime highs of 14-18°C arrive on moderate to fresh westerly winds.

Sunday night brings rain and drizzle to the west with clear spells elsewhere. Overnight lows drop to 6-10°C in light south-westerly breezes — the coldest night of the forecast period.

Monday turns dry and bright, with only patchy rain and drizzle possible along Atlantic coasts in the afternoon. Tuesday is currently expected to be a wet and windy day with widespread rain.

What about soil moisture and drying?

Soil moisture deficits in Leinster and east Munster currently range from 5mm to 39mm. Elsewhere across the country, soils sit saturated or close to saturation. Some poorly drained soils in the northwest are close to waterlogged.

Over the coming week, values are expected to decrease for most areas as rainfall builds. Met Éireann said the mixed or unsettled weather will produce mostly moderate or poor drying conditions. Mean air temperatures over the next seven days will sit between 13°C and 15°C. Mean soil temperatures will decrease slightly but stay above average.

Which regions face heaviest rainfall?

Rainfall amounts over the coming week will vary sharply by region. The west, north and midlands will see close to or below average totals. The south and east could see up to twice average levels.

That split defines who gets a workable spray window next week and who doesn't. Operators looking to apply crop protection products should plan around Monday's drier conditions where local forecasts allow.

Watch for Met Éireann updates through Sunday on whether the blight warning window extends, and for Tuesday's wet-and-windy signal, which could keep sprayers parked into midweek.