ITHACA, N.Y. — If you’ve got some ornamental plants or a home garden, move them indoors or break out the drop cloths and stakes. With rain coming to an end and high pressure moving in, cold Canadian air funneled into the region will drop temperatures low enough for a hard freeze across much of the area Sunday night into Monday morning.

Graphic courtesy of NWS Binghamton.

Your Weekly Weather

Let’s do a quick refresher before we jump into the weekly forecast. A hard freeze is when temperatures drop below the freezing point for a sufficiently long and severe period, enough to destroy seasonal vegetation and lead to ice formation in standing water and hard ground. This generally occurs between 25 °F and 28 °F. The low tonight in the city of Ithaca and along Cayuga Lake will be on the top end of that range, around 28-29 °F. However, most elevated areas and communities away from the moderating effects of the lake’s waters can expect temperatures to drop a couple degrees lower, into the mid 20s. That allows water in tender, growing plant cells to freeze, and as it freezes it expands and tears up the cells, ripping the plant to shreds a million microscopic times and thus killing the plant.

If the plant can be brought inside into a warmer space like a garage or a greenhouse, you’ll want to do that before heading to bed tonight. If that’s not an option, then keep the soil moist (wet soil holds daytime heat longer) and stake the ground so that you can throw a plastic tarp of drop cloth over the plants, like a blanket. The tarp can be removed after sunrise when temperatures start to warm up again. Another option is to throw down some straw, or if you want to upset your energy-conscious neighbors, dig out some non-LED lamps or Christmas lights and run them through the plot for a little extra warmth.

My phlox are not impressed.

If there’s any silver lining to this, it’s that this weekend’s rainmaker is finally pushing out. As the high pressure moves in from the northwest and its clockwise circulation pulls down that chilly air, skies will also clear out. For tonight, expect mostly clear skies and temperatures in the mid to upper 20s with calm winds.

However, those blue skies tomorrow morning will be fairly brief, as a weak, fast-moving shortwave disturbance pushes westward across the region. Mostly clear skies around daybreak will grow increasingly cloudy during the day, with temperatures getting into the mid 50s as mostly cloudy skies prevail by late afternoon. Some rain showers are likely to enter the western side of Tompkins County before sunset, but Ithaca and communities to the east will not see much until 8 PM or so, with a few hours of rain into Tuesday morning that should taper off in most places before sunrise. Lows Monday night will be in the mid 40s.

It’ll be a little warmer behind the shortwave, but still on the cool side for this time of the year, with mostly cloudy skies and highs in the upper 50s to close out April. A second system approaches from the west Tuesday night, and with it another round of rain for the early hours of Wednesday morning. Expect scattered rain showers and lows in the mid 40s.

The second system looks to be a more substantial area of low pressure passing over Michigan before changing course and passing over upstate New York, with a frontal boundary that will extend from the Northeast to Texas. This will result in extended rainy, unsettled conditions, though with the low to the west and then north, that will allow milder air to be advected into the region. Wednesday will have periods of rain and cloudy skies, with highs in the mid 60s. A more steady rain is likely overnight Wednesday, with lows in the low 50s. This looks to be an extended light rain, so while rain will be present throughout the day and night, total rainfall amounts will likely be no more than a quarter to half an inch.

For Thursday, the rain will persist into the mid-morning hours before most places start to dry out, and highs will make into the upper 60s under cloudy skies. Unfortunately, the drying period will be short, as a third system is likely to develop over the lower Mississippi River valley and trek northeastward along the frontal boundary, bringing more rain into the air late Thursday night, with rain winding down Friday morning after daybreak as the system moves eastward. Lows Thursday night will be around 50 °F.

Friday will be drier if a bit cooler. Plan for mostly cloudy skies, a few lingering rain showers, and a high in the low 60s. Clouds will begin to clear out later Friday, and with some larger breaks in the clouds and cooler air behind the system, temperatures will drop into the low 40s Friday night.

After a week of grey, dreary weather, the weekend will provide welcome respite, if a hair on the cool side. Expect upper 50s Saturday and low 60s Sunday, with mostly sunny skies. Saturday and Sunday night will be partly cloudy, and in the upper 30s and low 40s respectively.

Graphic courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking ahead into May, it’s looking like the first half of the month will be a little on the cool side, as a strong west-east flos in the jet stream keeps cooler air bottled up in the upper Midwest and Northeast, with a modest ridge over the Pacific Northwest. Most of the country, us included, is expected to see elevated chances for a wetter-than-normal early May, with excessive precipitation possible over the Lower Mississippi River valley.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.