I have enjoyed some nice May trips to Helsinki. Cool sometimes. Rain sometimes. Days reasonably long. I have not visited in April.

May should be the best time of year to visit these places. Most probably you will encounter nice, springlike temperatures, but be also prepared for cool temps and rainy days. You never know. May is warmer than April.

May is good time to visit St. Petersburg, especially late May when the white nights period starts. The fountains in Peterhof will be functioning (they don't begin until May) and it will be worth visiting the parks around the summer palaces.

Moscow should be nice, but expect a COLD wind blowing off the sea in St Petersburg.

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May I suggest doing the opposite?

Fly to Moscow, take a sleeper car on the late train(to SP. This pushes back your SP days and avoids a hotel night

19cruise80-We'll be taking a riverboat cruise St. Petersburg to Moscow May 24-June 4. Can you tell me about white nights? I've never heard of it, but sounds like we'll be there for it. Thanks.

I had to look this up, we too will be in Russia but too late for this event. We're in Moscow for 4 nights from April 29, train to SP and then 4 nights there.

The White Nights Festival in St. Petersburg, Russia is an annual international arts festival during the season of the midnight sun. The White Nights Festival consists of a series of classical ballet, opera and music events and includes performances by Russian dancers, singers, musicians and actors.

www.balletandopera.com/festivals/stars-of-the-white-nights-festival/?sr=gsu&kw=white%20nights%20st%20petersburg#an1

IMO it's never a silly time to visit these places. There isn't a spring season as such, it seems to go almost straight from winter to summer and summer comes early. May is a holiday month for Russians and some businesses close for the first two weeks, or at least are limited. The sun doesn't set until about 10pm early May in St Petersburg and then gets later and later until it doesn't set until midnight but there is light all night long. This is the time to party and if you get stuck on one of the islands partying, you might not be able to get back to your hotel until after 5am when the bridges open again.

Visiting St. Petersburg during the White Nights is very special - but can be very expensive!

The description aussiedreamer gives is undoubtedly correct, but I believe the thing that really defines the White Nights is what Odin mentions - the near absence of dark.

I was fortunate enough to be there during the longest days of the year, and had the disorienting experience of seeing the sun set in a position that seemed more like the north than the west, and then to see it rise a a few hours later just a bit further east. It never got completely dark - there was just a prolonged period of dusk merging into dawn. People were out enjoying themselves and their beautiful city well into the early hours of the morning. And there was some kind of fluffy white seed-like thing - I think from a kind of tree that is common in the city - that burst out almost like dandelion around that time. Youngsters and teenagers and even some people a bit older were gathering it up and then setting a match to it -- it would vanish with a POOF.

For sunset and sunrise times, see:
http://www.timeanddate.com/worldclock/astronomy.html?n=352&month=6&year=2013&obj=sun&afl=-11&day=1

IMHO, if you have the chance to visit St. Petersburg at any time, do. If you have the chance to visit St. Petersburg during the White Nights, do it!!!

It's from a poplar tree, it covers the cities like snow in summer.

Thanks for the info, Odin. It did seem like snowfall!

We did the same trip last May. We arrived in Helsinki on April 26 for two nights and then took the train to St. Petes and then Moscow. It was crisp to be sure in Helsinki and St Petes but blue skies and we just wore appropriate clothing.

We purchased wool coats at our local second hand store and then left them in Russia so as not to lug them to Turkey with us, as it was of course much warmer there. That worked out perfectly for us.

We loved Russia!.