Severe Thunderstorm watches in effect for much of GTA except lakeside areas, indicating potential of severe weather development later this afternoon/evening.

Here's the text from Environment Canada as of 5.04PM -- warnings listed first, watches listed underneath.

WWCN11 CWTO 212104
SEVERE WEATHER BULLETIN
ISSUED BY ENVIRONMENT CANADA
AT 5:04 PM EDT THURSDAY 21 JUNE 2012.
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WATCHES/WARNINGS IN EFFECT FOR SOUTHERN ONTARIO...

SEVERE THUNDERSTORM WARNING FOR:
=NEW= WOODSTOCK - TILLSONBURG - OXFORD COUNTY
=NEW= CALEDON
=NEW= GUELPH - ERIN - SOUTHERN WELLINGTON COUNTY
=NEW= BARRIE - COLLINGWOOD - HILLSDALE
=NEW= MIDLAND - COLDWATER - ORR LAKE
SARNIA - LAMBTON
LONDON - MIDDLESEX
GODERICH - BLUEWATER - SOUTHERN HURON COUNTY
STRATFORD - MITCHELL - SOUTHERN PERTH COUNTY
LISTOWEL - MILVERTON - NORTHERN PERTH COUNTY
KITCHENER - CAMBRIDGE - REGION OF WATERLOO
MOUNT FOREST - ARTHUR - NORTHERN WELLINGTON COUNTY
DUFFERIN - INNISFIL
ORILLIA - LAGOON CITY - WASHAGO.

SEVERE THUNDERSTORMS ARE IMMINENT OR OCCURRING IN THE AREA
UNTIL 7:00 PM EDT. THESE STORMS MAY PRODUCE LARGE HAIL,
DAMAGING WINDS OR HEAVY RAINFALL. REMEMBER THAT SOME SEVERE
THUNDERSTORMS CAN ALSO PRODUCE TORNADOES.

EMERGENCY MANAGEMENT ONTARIO RECOMMENDS TAKING COVER
IMMEDIATELY WHEN THREATENING WEATHER APPROACHES.

SEVERE THUNDERSTORM WATCH FOR:
WINDSOR - ESSEX - CHATHAM-KENT
SARNIA - LAMBTON
LONDON - MIDDLESEX
WOODSTOCK - TILLSONBURG - OXFORD COUNTY
HALTON HILLS - MILTON
MISSISSAUGA - BRAMPTON
CALEDON
VAUGHAN - RICHMOND HILL - MARKHAM
NEWMARKET - GEORGINA - NORTHERN YORK REGION
UXBRIDGE - BEAVERTON - NORTHERN DURHAM REGION
STRATFORD - MITCHELL - SOUTHERN PERTH COUNTY
LISTOWEL - MILVERTON - NORTHERN PERTH COUNTY
WATERLOO - WELLINGTON
DUFFERIN - INNISFIL
BARRIE - ORILLIA - MIDLAND
PETERBOROUGH - KAWARTHA LAKES
BANCROFT - BON ECHO PARK
HALIBURTON - MINDEN - SOUTHERN HALIBURTON COUNTY.

CONDITIONS ARE FAVOURABLE FOR STRONG THUNDERSTORMS TO DEVELOP
THIS AFTERNOON AND EVENING. SOME OF THIS STORM COULD REACH
SEVERE LEVEL WITH TORRENTIAL DOWNPOURS, LARGE HAIL AND DAMAGING
WINDS.

THIS IS AN ALERT TO THE POTENTIAL DEVELOPMENT OF SEVERE
THUNDERSTORMS WITH LARGE HAIL, DAMAGING WINDS OR HEAVY
RAINFALL..MONITOR WEATHER CONDITIONS AND LISTEN FOR UPDATED
BULLETINS.