OTTAWA -- A heat warning is in effect on this first day of summer.

Summer officially arrives in Ottawa at 5:43 p.m.

With the heat warning, expect hot temperatures and stifling humidity through the day.

Environment Canada's forecast for Saturday includes sunshine in the morning, a sun/cloud mix in the afternoon and a 30 per cent chance of showers with the risk of a thunderstorm. The high is 34°C with a humidex of 39 and a UV index of 9, or very high.

Not much relief comes at night. The overnight low is 20°C under a clear sky.

Expect another stuff day on Sunday, with a few clouds and a high of 33°C with a humidex of 39.

Monday's outlook is partly cloudy with a 40 per cent chance of showers and a high of 31°C.

Cooling centres open

The City of Ottawa has opened five emergency cooling centres for anyone seeking some relief from the heat.

The cooling centres are open from 11 a.m. to 7 p.m. Saturday and Sunday and are located at:

  • Ron Kolbus Lakeside Centre - 102 Greenview Avenue
  • Hunt Club Riverside Park Community Centre - 3320 Paul Anka Drive
  • Hintonburg Community Centre - 1064 Wellington Street West
  • Sandy Hill Community Centre - 250 Somerset Street East
  • St. Laurent Complex - 525 Cote Street

There are also many other options for anyone looking to cool off, including splash pads, beaches, and newly reopened malls.

Staying cool during the heat wave

Ottawa Public Health offers tips to stay cool during the heat wave:

  • Drink plenty of water and avoid alcohol and caffeine
  • Avoid heavy outdoor activity
  • Wear a hat, light and loose-fitting clothing, sunscreen and sunglasses when outside
  • Bring an umbrella and water when you leave home
  • Cool off in an air-conditioned space
  • Cool off in the shade or at a park or greenspace
  • Use a fan and mist your skin with water
  • Take cool baths and showers as often as needed
  • Keep your home cool by closing blinds and curtains on any windows facing the sun