well I am a zone ahead of you so I know we experience things a bit differently, but I will jump in and tell you what I did this year. I was determined to have my tomatoes and peppers out earlier than ever. To do this, I planted out the first batch in containers so that I could bring them under cover if necessary. I had planned to plant in the ground with a plan to be able to cover on cold nights--stakes that I could wrap with plastic and cloth cover.
My first tomato plants went out first week of May, which is very, very early even for this zone. Peppers were not out as early as they are a bit more tender.

How cool are your nights getting? Are you able to protect them if nights get too cool? How hardened off are your plants? Once they are fairly hardened off, they can take cool nights, but not a frost/freeze of course.

sorry, no advice, just thoughts and suggestions. :-)

P.S.--I only got a few tomatoes out this early (in case I lost them) and I still have some to plant as I am planting in stages, but some of my tomatoes have flowers. This is VERY early.

Hi Greylady-gardener: I see you are also trying to get a head start. I am so far ahead that my peppers are already starting to bud. A pity there are no pollinators for them. The low temperatures are between 8 and 11 for the next week and the highs are betweem 17 and 18 with a couple of days at 20. It seems a bit cold to me, and I have never got a real definitive temperature at which it is safe to plant out. I have been putting my seedlings out daily for at least a week now, but I did not put them out yesterday because it was very cool all day. Actually, almost all my peppers will be grown in pots (the hot ones anyway) so perhaps I could try with a few of them, but the tomatoes have suffered an attack of spider mites and I really want to get them in the ground. Let me know if you think these temperatures are safe or I'll have to wait another week. Looks like my early start was for naught.

Hi,

I used to live in Ottawa for years and moved to Sharbot Lake in 2010. I'm in the same zone. You and I are a zone 5a. I have just planted my tomato plants and have only baby pepper plants but have planted them out as well yesterday after hardening them off.

We are technically out of the frost dates. Given that we are experiencing weather that flips from cold to hot I'm taking advantage of the cooler day (like yesterday and today) to put as many plants in that I can (all hardened off). It's much less stress to plant out on a cooler day then the hot days.

That's my 2 cents worth and my experience. I used to live in Tanglewood, Nepean in Ottawa and years ago near the Experimental farm. Mainly Ottawa west (now central).

Enjoy your garden!

Hi Mcpeg: I am so happy that you replied, that you are in the same zone as I am and doing the same things. It really puts my mind at ease about these seedlings which I have spent so much time and energy on. I put them out for sometime today and came home in the early evening to find it was quite cool so at first I covered them, then I put them under my deck table and covered it with sheets and my tarp; finally I put them in my unheated garage which was surprisingly warm. I started hardening them off May 21, and plan to keep them out all day from now on, so they should be fine. Sunday should be a good day: cloud and isolated showers are predicted so I'll aim for that. I live in what was once Nepean, very near to Andrew Haydon Park and I know the areas you mentioned. Thanks ever so much and do enjoy your garden. You made my day!!!